Simple metadata queries
Adds support for retrieving metadata that matches all key/value pairs in a query object. This is a minimal version of #222 that can be extended if we need other query capabilities.
See merge request !187
Rotate crash fix
The problem was that two controllers were trying to unbind the Briar service where of course only one was needed.
I did the following
* Restructured the relevant Controllers
* Made a more permanent solution so that the last fragment will always be reloaded on config changes and Activity restarts.
Closes#386
See merge request !183
Add forum avatars to list of available forums

Closes#374
See merge request !182
Forum Avatars
These new forum avatars are using the first letter of the forum and calculate the background color from forum's group ID.
Closes#337

See merge request !178
Start plugins asynchronously
This prevents other services from getting stuck behind the plugin manager while the Tor plugin is starting, which takes several seconds. The plugin manager waits for each plugin to start before stopping it.
I've also added some canaries to plugins and services to ensure instances aren't started more than once.
See merge request !181
Poller refactoring, replace Timer with ScheduledExecutorService
* Replace Timer with ScheduledExecutorService (closes#258)
* Move automatic connection logic from PluginManager to Poller
* Reschedule polling when connections are opened or closed, making the poller more responsive to reductions in the polling interval
See merge request !180
274 code encapsulation
The goal of this branch is to better compartmentalize, structure and simplify the code in the Android module. It does this via the following techniques:
* Extended use of Dagger by introducing a component for Activities that injects, among other things, SharedPreferences and Fragments. The latter makes it possible to mock fragments more easily and letting Dagger automatically handle its injections.
* Decouple Briar API code, from the activities and Fragments, and encapsulate in re-usable Controller classes
* Introduce a UI-thread App event bus that the Helper classes use to communicate with Activities & Fragments.
* Define the testing methods in the briar-android module per Robolectric and Mockito
NOTE! Don't be alarmed if you see the contact introduction message one more time, one of the changes was to purify UI shared preferences from the Briar shared preferences, which now only contain preferences related to the API and it's usage.
closes#274
See merge request !130
Forum Sharing Client UI
This changes `ShareForumActivity` to use two fragments to facilitate
forum sharing with the new Forum Sharing Client backend.
The `ContactSelectorFragment` allows the user to select a
number of contacts. If there is an ongoing sharing session or the forum
is already shared with the contact, it is disabled in the list. If there
is at least one contact selected, a button appears in the toolbar that
brings the user to the `ShareForumMessageFragment` where the user can
write an optional message to be send along with the invitation.
After sending an invitation, the user is brought back to the forum that
she shared and there is a snackbar showing up briefly to indicate the
successful invitation.
The invitation is shown along with the message within the private
conversation of each contact. The person who shares the forum also sees
the invitation and the message as outgoing messages that also display
the current status of the messages.
A notification is shown like for other private messages as well.
Please note that this commit does not include a way for users to respond
to invitations. This is in MR !172. Both MRs are based on the new backend in !170.


See merge request !171
Modernize AvailableForumsActivity
Turn list of available forums into a `BriarRecyclerView` with XML layout.
Allow to respond to forum invitations from the list of available forums.
The user can either accept or decline an invitation.

See merge request !172
This changes `ShareForumActivity` to use two fragments to facilitate
forum sharing with the new Forum Sharing Client backend.
The `ContactSelectorFragment` allows the user to select a
number of contacts. If there is an ongoing sharing session or the forum
is already shared with the contact, it is disabled in the list. If there
is at least one contact selected, a button appears in the toolbar that
brings the user to the `ShareForumMessageFragment` where the user can
write an optional message to be send along with the invitation.
After sending an invitation, the user is brought back to the forum that
she shared and there is a snackbar showing up briefly to indicate the
successful invitation.
The invitation is shown along with the message within the private
conversation of each contact. The person who shares the forum also sees
the invitation and the message as outgoing messages that also display
the current status of the messages.
A notification is shown like for other private messages as well.
Please note that this commit does not include a way for users to respond
to invitations.
Turn list of available forums into a BriarRecyclerView with XML layout.
Allow to respond to forum invitations from the list of available forums.
The user can either accept or decline an invitation.
New List of Forums
The adapter of the `ForumListFragment` has been changed into a
`BriarRecyclerView` and all its code has been adapted and simplified
accordingly.
All UI of the forum list is now defined in XML layouts. This enabled me to move the snackbar into onCreate().
Before:

After:

See merge request !175
Try harder to connect to contacts
* When an outgoing connection is lost, try to reconnect to the contact straight away
* Use periodic polling for Tor, regardless of whether our hidden service descriptor has been published
* Reduce polling intervals for all plugins (this can be reverted if we solve the connectivity issues)
Closes#262, #314. Hopefully helps with #361.
See merge request !177