Also react to incoming group invitations

* Improve wording so contacts know they need meet up to scan
  and scan each other's codes
* Use consistent progress bar styles

and maintain keyboard state when hiding view.

This commit also moves various blog classes into their own packages and
makes the required visibility changes.

All text that can be generated by users will show emoji from the
shipped sprites.

For all messages and posts, the custom emoji keyboard is now available.

This also disables menu actions rather than hiding them and thus
closes #677

Included is a fix for a regression that was not showing the keyboard
automatically in forums and thus
closes #676

The app _name string is marked as non-translatable and the new_identity_item string no longer exists.

When the user enters a private conversation after adding her second
contact, an onboarding screen will be shown highlighting the possibility
of introducing the contacts to each other.

Add functionality to save and restore recently used Emojis

Update emoji and add new categories based on AOSP's XML file