This also adds two integration tests and improves some small details

Also react to incoming group invitations

Also close keyboard when returning from message fragment

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

added a cache to the IdentityManager, changed its signature, modified when and where the author is stored

made the author creation single-threaded again in the LifecycleManager, removed redundant code

and turn them into a regular string.

Also removes support for anonymous forum posts.
Closes #698