add documentation for meshquality filter

Documentation for meshquality filter, including two new tables of options.

@kmorel I tried hard to follow norms, but probably messed up somehow. I know tables are hard to maintain, but I am hoping I "did good", esp. because I am within margins and I broke it up across two pages in a way that did not require special LaTeX packages. (I did a lot of experimenting to find the most maintainable method here.)

merged

mentioned in commit 8fca9792