Support for generating docs for type providers

This is a very hacky solution, as FCS doesn't support this. The xml docs of type providers don't even go to the generated xml doc from the compiler, you only get a bunch of `<member name=""></member>`.
What this does is look at the xml docs and get the names of the static params, but it's not able to get neither the type, default value or optionality. And if the xmldocs don't document all the parameters, they won't go into the fsharp.formatting generated docs