fixed stuff
Merge branch 'Natascha' into somewhatBeautyQueen
added observable constructor + using it AND videos adding works now (selecting doesnt)
added method to add a video with a path to a metadatafile - interfaces changed
added some checks to addVideo(...)
oops... forgot some brackets again
implemented overlaycontroller (incomplete)
added method insertOverlayWithPixelDiff
made view state not saveable
Committed unommitted changes ... sorry
Merge branch 'Natascha' of https://github.com/V02460/CTT
Merge branch 'Natascha' into somewhatBeautyQueen

Conflicts:
	CTT/ExtendedVideoListController.h
fixed null poiner
changed in observable now public + changes in project and xmlloader
Fixed all Operations
Merge branch 'master' into somewhatBeautyQueen

Conflicts:
	ctt/ViewState.cpp
	ctt/XMLLoader.cpp
Implement DifferenceTimeline
Merge branch 'Natascha' into viewDieZweite

Conflicts:
	CTT/AnalysingOrderingWidget.cpp
	CTT/AnalysingOrderingWidget.h
	CTT/ExtendedVideoAddedOperation.cpp
	CTT/ExtendedVideoAddedOperation.h
	CTT/ExtendedVideoRemovedOperation.cpp
	CTT/FilterListViewElement.cpp
	CTT/FilterListViewElement.h
	ctt/ExtendedTimeline.h
	ctt/ViewState.cpp
	ctt/ctt.vcxproj
Fix build errors