Eventbus the prefs events.

Depends-On: Ia3a86ce30a3ad96c2c67597dba341b2b10162c8e
Change-Id: I27e1059cc3228013d30bab85549434dea28f236c
Reviewed-on: http://gerrit.dmdirc.com/3418
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Chris Smith <chris@dmdirc.com>