COMP: Add Slicer_INSTALL_DEVELOPMENT option - By default OFF
For now, this is *just* a regular variable instead of being a CMake Option. In order to be able to provide a developer package. More work is required. git-svn-id: http://svn.slicer.org/Slicer4/trunk@16361 3bd1e089-480b-0410-8dfb-8563597acbee