Add Snackbar and Toolbar Button to Forum List

This commit is a small change that replaces the custom UI elements in
the forum list with a Snackbar and an Toolbar menu.

Addresses one part (2b) of #305

briar-android/res/layout/activity_with_loading.xml

@@ -22,15 +22,13 @@
 		<FrameLayout
 			android:id="@+id/content_fragment"
 			android:layout_width="match_parent"
-			android:layout_height="match_parent"
-			android:background="@color/default_background"/>
+			android:layout_height="match_parent"/>
 
 		<RelativeLayout
 			android:id="@+id/container_progress"
 			android:layout_width="match_parent"
 			android:layout_height="match_parent"
 			android:layout_gravity="center"
-			android:background="@color/default_background"
 			android:visibility="invisible"
 			tools:visibility="visible">
 

briar-android/res/menu/forum_list_actions.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<menu
+	xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto">
+
+	<item
+		android:id="@+id/action_create_forum"
+		android:icon="@drawable/ic_add_white"
+		android:title="@string/create_forum_button"
+		app:showAsAction="ifRoom"/>
+
+</menu>

briar-android/res/values/color.xml

@@ -31,10 +31,11 @@
 	<color name="briar_text_primary_inverse">#ffffff</color>
 	<color name="briar_text_secondary">#333333</color>
 	<color name="briar_text_tertiary">#333333</color>
+	<color name="briar_button_positive">#06b9ff</color>
+	<color name="briar_button_negative">#ff0000</color>
 
 	<!-- this is needed as preference_category_material layout uses this color as the text color -->
 	<color name="preference_fallback_accent_color">@color/briar_accent</color>
-	<color name="default_background">#ffffff</color>
 	<color name="default_separator">#000000</color>
 	<color name="default_separator_inverted">#ffffff</color>
 	<color name="menu_background">#FFFFFF</color>

briar-android/res/values/strings.xml

@@ -77,6 +77,7 @@
 		<item quantity="one">%d forum shared by contacts</item>
 		<item quantity="other">%d forums shared by contacts</item>
 	</plurals>
+	<string name="show_forums">Show</string>
 	<string name="unsubscribe">Unsubscribe</string>
 	<string name="unsubscribed_toast">Unsubscribed</string>
 	<string name="no_forum_posts">No posts</string>

briar-android/res/values/styles.xml

@@ -67,13 +67,13 @@
 	<style name="BriarButton.Default"/>
 
 	<style name="BriarButtonFlat.Negative" parent="Widget.AppCompat.Button.Borderless">
-		<item name="android:textColor">#ff0000</item>
+		<item name="android:textColor">@color/briar_button_negative</item>
 		<item name="android:textSize">@dimen/text_size_medium</item>
 		<item name="android:padding">@dimen/margin_large</item>
 	</style>
 
 	<style name="BriarButtonFlat.Positive" parent="Widget.AppCompat.Button.Borderless">
-		<item name="android:textColor">#06b9ff</item>
+		<item name="android:textColor">@color/briar_button_positive</item>
 		<item name="android:textSize">@dimen/text_size_medium</item>
 		<item name="android:padding">@dimen/margin_large</item>
 	</style>