Merge pull request #212 from csmith/master

Fix remaining null-passing method.
Convert ContactListListener to events.
Tidy up NickList + Renderer.
Merge pull request #213 from greboid/tidying

Convert ContactListListener to events.
Merge pull request #214 from greboid/tidying3

Tidy up NickList + Renderer.
Fixups for GroupChatUser.
Revert AwayColoursManager changes.
Break ContactListCommand.
Merge pull request #215 from greboid/tidying2

Fixes for latest GroupChatUser changes.
Remove TopicChangeListener. Add Topic to topic events.
Merge pull request #217 from greboid/tidying2

Remove TopicChangeListener. Add Topic to topic events.
Fix some nullable annotations in debug plugin.