Modify ghost cells generator filter to also work with topologically regular grids
This is useful for loading silo files through the VisIt bridge where they come in as a composite dataset of rectilinear grids. I can convert them to a single rectilinear grid using a programmable filter but in parallel I don't have ghost information available for filters that need them.
This could also be useful for Catalyst for simulation codes that produce topologically regular grids.
I'm marking this as a 5.8 milestone as this is a semi-urgent need for some users. Please let me know if this doesn't seem reasonable for the 5.8 release since I'm not sure how soon our funding will be in place.