BUG: 3DMeshMetric tests were failing

-File paths were hard coded
-Tests were not setting certain values before checking them
ENH: ModelToModelDistance labels have been updated to be more meaningful
STYLE: Addition of a readme file and a license file
COMP: Remove support for VTK5 for ModelToModelDistance and remove support to use MeshValmetlib to compile ModelToModelDistance
ENH: Addition of an option to save the name of the target file in the names of the fields in the output file.
ENH: When computing corresponding point distance, ModelToModelDistance now prints number of points of each model if their number of points do not match.
BUG: The flags of ModelToModelDistance have changed to more meaningful ones. The flags in the tests have been changed consequently.
BUG:  ${Slicer_LAUNCH_COMMAND} had been removed from the test command line in the fear that this would create issue to run the tests when the project is not built as a Slicer extension. However, since this variable will not be defined in such a case, it will just be empty and be ignored.