ENH: extend the model maker to take a template model hierarchy as an argument.

Also added a test, and adjusted the testing to use different mrml files
per test as the new test is going to modify the mrml file.

If the model maker is passed a template model hierarchy scene file that
has model hierarchies with the same names as the colors used in the
input label map volume color node, the output models are placed in the
hierarchy as associated nodes. The 1:1 hierarchy nodes are set hidden
as it will be easier for a user to create a template hierarchy in the Models
GUI with all the nodes not hidden from editors.

Leaving this an an advanced option hidden under the Debug panel until further
user testing can be done and more templates provided. To use this feature, one
currently needs to craft hierarchies by hand in the Models GUI, save the scene,
then edit the mrml file to remove scene views and other unneccessary
mrml nodes. The plan is to provide templates for the most used color
tables that Slicer provides in the Base/Logic/Resources/ColorFiles
directory.

From work at the 2013 winter project week
http://wiki.na-mic.org/Wiki/index.php/2013_Project_Week:ColorHierarchies

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21665 3bd1e089-480b-0410-8dfb-8563597acbee