Update input refactor

@aashish24 @doutriaux1 @sankhesh @chaosphere2112

Done with the update_input refactor and ported the VTK pipeline-related stuff from VTKPlots.update_input into the pipeline classes.

There was a unfinished/nonworking/untested bit of update_input that was for vector plots that gets removed by this PR. I'll push another branch (no PR) shortly and file a bug for this.

I ended up leaving the map returned from pipeline.plot(...) in and just fixed the leaks that were causing the segfaults. Now Canvas.close() must be called in user scripts to avoid the crashes. These can be further refined in the future as needed. See af6eafd0 and dd81ee3a. Once the rest of the leaks that are preventing canvases from cleaning up when going out of scope are cleaned up, this caveat can go away.

vcs2vtk.doWrap is now wrapped in a VTK filter so that it can be called as part of the VTK pipeline execution. See 457c5fd3 to see how this can be done for other parts of the code that may need it down the road.

Goes with UV-CDA