Document the full usage and syntax of object filter in lib/objectfilter.py

Please either add a link to the full language syntax specification or flesh out the examples in the docstring of this file.

i.e. enumerate all the operations as their textual counterparts. e.g. 'address contains "string"', etc.

Basically, format out what OP2FN has in it.

Bonus points for describing the rest of the lexer in EBNF somewhere.