COMP: Prevent windows build error shortening DisplayableManager directory

"MRMLDisplayableManager" sub directory associated with module has been
changed into "MRMLDM" to prevent issue related to path length limitation.

See http://slicer-devel.65872.n3.nabble.com/No-Windows-nightly-package-since-May-2-tp4028642p4028646.html

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21987 3bd1e089-480b-0410-8dfb-8563597acbee