Proposal: Remove VtkGlue from ITK, and add ITKVtkGlue as a remote module

To streamline maintenance, I suggest to (1) remove the directory Modules/Bridge/VtkGlue from ITK source tree and (2) add a remote module referencing https://github.com/InsightSoftwareConsortium/ITKVtkGlue

Long ago, @matt.mccormick and I discussed this and agreed this should be done. I forgot whether there are some blockers for this, or it was just never reached top of the priority list. If you have time for this migration JC, go for it. But probably wait for a reply from Matt, to avoid potential duplication of work.

Yes, the remote module needs additional improvements before we can use it to replace the module in the ITK repository. There was some work to build the module Python cross-platform, but the vtk interface kept changing and it was complicated.