[XML Markers] Add Code Generator for Filter Classes

[AsherGlick]

The generator should automatically create any of the "filter" classes, such as the mount filter from the mount filter docs.

This implementation will be similar to how #67 works, where a stringy value is matched to a particular class variable being set, however for filters all the class variables that will be set are bools, and there is no other type that they can be.

The Filter base class should then be removed.