Add two triggers for button override.

It's a quite simple trigger.
I thought I could use the Activity integration but, I wasn't sure that it was the right place.
Merge pull request #1306 from coder4life/master

Kunena30/Joomla30 Backend: Added top level view titles.
Merge pull request #1194 from obsidev/TriggerButtons

Add two triggers for button override.
#1300 Some Buttons missing their corresponding images
#1302 Visual issues with Move Messages of a user
Merge pull request #1317 from xillibit/k30_img_button_backend

#1300 Some Buttons missing their corresponding images
Merge pull request #1320 from xillibit/k30_bugs3

#1302 Visual issues with Move Messages of a user
Merge branch 'master' of git://github.com/Kunena/Kunena-2.0