feat(service): more mathtype fixes, this time in a clean branch

Trying to get a cleaner branch to make the changes more clear!

This changes the MathType processing code to deal with inline equations and edge situations found in a particular document from Amnet. Sometimes LaTeX was being exported that included inline MTEF XML, which contains positioning and color data that can't be represented in vanilla LaTeX; this strips that out. This is not stripping out all XML tags (which might look very much like valid LaTeX); it only strips out the tags that were represented in that document. I've asked for more sample MathType documents to see how often this issue comes up, but haven't yet received them. This does post a warning if it does encounter something in LaTeX from Mathtype that looks like XML so that we can better diagnose this issue in the future.

All of this is behind the math flag, so it should not affect anything that's not using this (or anything that's not converting WMF to LaTeX).