Tab customization & direct messages tab (#1012)

* custom tabs

* custom tabs interface

* implement custom tab functionality

* add database migration

* fix bugs, improve ThemeUtils nullability handling

* implement conversationsfragment

* setup ConversationViewHolder

* implement favs

* add button functionality

* revert 10.json

* revert item_status_notification.xml

* implement more menu, replying, fix stuff, clean up

* fix tests

* fix bug with expanding statuses

* min and max number of tabs

* settings support, fix bugs

* database migration

* fix scrolling to top after refresh

* fix                                 bugs

* fix warning in item_conversation

app/src/main/res/xml/account_preferences.xml

@@ -6,6 +6,10 @@
         android:key="notificationPreference"
         android:title="@string/pref_title_edit_notification_settings" />
 
+    <Preference
+        android:key="tabPreference"
+        android:title="@string/title_tab_preferences" />
+
     <Preference
         android:key="mutedUsersPreference"
         android:title="@string/action_view_mutes" />