Merge branch '153-forum-sharing-with-selected-contacts' into 'master'

Improve Forum Sharing UI when sharing with selected contacts

When sharing only with chosen contacts, checking the contact's checkbox
and pressing Done nothing happens and the forum is not shared. An
additional click on "Share Forum" is necessary to actually share.

This behavior is fixed with this change.
Now, clicking 'Done' immediately shares the forum.

Closes #153

See merge request !20