Feature: Multiple Backgrounds in an Activity

--Multiple Backgrounds when the user has set different
Widgets in Virtual Desktops (Workareas ;)
Merge branch, support for multiple backgrounds

Conflicts fixed:
	components/models/activityitem.cpp
	components/models/activityitem.h
	components/subengines/activitymanager.cpp
	components/subengines/workareasmanager.cpp
	dataengines/workareaengine.cpp
	dataengines/workareaengine.h
	qdbus/CMakeLists.txt
	qdbus/WorkareaManager.cpp
	qdbus/WorkareaManager.h
	qdbus/client/workareainterface.h
	qdbus/mechanism/findwallpaper.cpp
	qdbus/mechanism/findwallpaper.h
	qdbus/org.opentoolsandspace.WorkareaManager.xml
	qdbus/workareainfo.cpp
	qdbus/workareainfo.h
disabled hot corner because it was creating kwin crashes