Revert "Roster: Fixed roster displaying only one line of info."

This reverts commit d7238451a251d85be98df3500986b3d3c64a8ddc.  With
current version of gtk+, this bug is fixed without this commit.

Conflicts:
	lib/engine/gui/gtk-frontend/roster-view-gtk.cpp
TODO: More notes.
Actor: Added method to disable/enable action by name.
Action: Added the possibility to create a disabled action + cleanup.
Actor: Added method to get ActionPtr by name.

Also refactorised code.
Opal::Account: Moved Heap actions to the new Actor mechanism.