* removing screen border visible on small screens
* showing noticeable error message on wrong password input
* showing keyboard again after entering wrong password
* making lost password link easier to recognize as link
* renaming keyboard toggle method from 'hide' to 'toggle'
This will allow any activity to show the expiry warning and password
prompt, and to start and stop BriarService.
SplashScreenActivity, SetupActivity, ExpiryActivity and PasswordActivity
are special cases.
This partially fixes dev task #40. CreateIdentityActivity is also called
from AddContactActivity, but that's likely to change soon so I'm not
going to fix it now.