Fixes OSX SDK locations

CMAKE_OSX_SYSROOT is no longer FORCEd.
Looks for both locations (/Application/... and /Developer/...) for SDK versions.
merged master back in, confirmed works on 10.8/5.1.1
Merge remote-tracking branch 'devel/vcs_isofill_fixes'
Merge remote-tracking branch 'devel/vcs_gm_with_cdtime'

Conflicts:
	Packages/vcs/Lib/vcs2vtk.py
Merge branch 'osx-sdk-locations'
Merge branch 'default-packages'
Updated metrics package to latest devel tag
Merge branch 'uvcmetrics_devel_for_beta' into devel