add quitAction with strg+q shortcut; fix some menuroles for mac; add strg+o shortcut to open
ref #80 fix window state recovery
ref #80 fix alignment of dock widgets in mac
ref #80 a little tweak
ref #9 loads CWD in FileExplorer on startup | synchronizes opening files in Explorer with expanding trees in Navigator
Merge branch 'master' of github.com:cgcostume/cgsee
Merge remote-tracking branch 'origin/master' into menu_improvements

Conflicts:
	libs/gui/fileNavigator.cpp
Merge pull request #80 from cgcostume/menu_improvements

Menu Improvements and Window State Recovery
Merge branch 'master' into scenegraph_2