COMP: Remove now obsolete patching of BRAINSTools ExternalData module

Considering both projects now use the same version of the module, it is
not required anymore to copy it.
See the associated BRAINStools issue for more details: https://github.com/BRAINSia/BRAINSTools/issues/3

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22904 3bd1e089-480b-0410-8dfb-8563597acbee
COMP: Do not force BRAINSTools options to ensure they can overwritten

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22905 3bd1e089-480b-0410-8dfb-8563597acbee
ENH: Extend 'Slicer_RemoteModule_Add' to accept list of cache options

When the VARS argument is set to a list of variable of the form:

  <name1>:<type1>=<value1> [<name2>:<type2>=<value2> [...]]

For more details, see inlined documentation.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22906 3bd1e089-480b-0410-8dfb-8563597acbee
COMP: Simplify how BRAINSTools project options are specified

Source repository, revision and associated CMake options are not
all set in a single location.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22907 3bd1e089-480b-0410-8dfb-8563597acbee