moved resources group creation from Engine to bsa component
register resources locations on editor startup
added Preview submenu item; fixed View issues regarding exterior cells
moved test cube from SceneWidget to WorldspaceWidget
prewview subview
use proper title for reference prewview subviews (avoid internal ID)
less random camera start position
consider scale and orientation when previewing reference
adjusted the far clip distance
Merge branch 'preview' of https://github.com/zinnschlag/openmw into Editor-Dialog

Conflicts:
	apps/opencs/CMakeLists.txt
	apps/opencs/view/world/subviews.cpp
added preview button