Also fixed a couple of bugs.

Switched AppBus for ResultHandler, Controller for Helper. Added the basics for LifecycleControllers and implemented it for BriarActivity and NavDrawerActivity

This also introduces constants for the GROUP_ID, FORUM_NAME and
MIN_TIMESTAMP as they were used for the two buttons.

Closes #313

This closes #204

Thanks to the team that audited CryptoCat for this idea. :-)

Very important stuff.

Fixes bug #42.

Hopefully this gives users a better understanding of whether their
messages and contacts are accessible than "Briar is running" and "Quit".

This avoids a possible problem where the app expires while it's running
and every activity shows the expiry warning, leaving the user with no
way to quit.