Allow escape comma in spark files

I'm not 100% sure if we want to do this, but I was thinking it might make sense to unify our parsing of input file lists and doing so in such a way as to allow files with ","s in them. I don't think its urgent (unless someone has a library which needs a file with that name in it which I imagine is unlikely) but seems like it might be reasonable (maybe in the 3.0 timeframe since it could change the meaning of currently configured strings).