COMP: Non-Slicer Builds failed due to missing components.

The ITK required components in slicer build ITK with VTK glue. This is not
necessary for BRAINSTools, so avoid the ITKVTKGlue options when not building
for slicer.
ENH: Add ReferenceAtlas and MD5 signatures

The ReferenceAtlas was previously stored in SVN, but
that solution was very combersome and expensive (from a
disk usage and network burden cost) to maintain for
nightly builds.

By using MIDAS, all the object files can be cached
on a local mount point by "export ExternalData_OBJECT_STORES=<>"
environmental variables.
ENH: Fix install materials.