Merge branch '426-forum-improvements' into 'master'

Forum improvements

Forum Activity improvements:

* Orientation changes now restore the activity properly, e.g. input text and state is retained
* Snack bar is now, when appropriate, clickable
* The bottom divider is no longer visible for the bottom entry
* Code refactoring for improved simplicity and less redundancy
* Timestamp check to ensure that new posts are not older than the latest post

Closes #426 
Closes #423 
Closes #424 

See merge request !218