Make Filter Clause Generic

[simlu]

Function:
https://github.com/GetintheLoop/painless-sqlalchemy/blob/develop/painless_sqlalchemy/core/ModelFilter.py#L132

This can be greatly simplifies by using:
https://github.com/zzzeek/sqlalchemy/blob/master/lib/sqlalchemy/sql/visitors.py

examples:
https://github.com/zzzeek/sqlalchemy/blob/master/lib/sqlalchemy/sql/util.py#L120
https://github.com/zzzeek/sqlalchemy/blob/master/lib/sqlalchemy/sql/util.py#L267
https://github.com/zzzeek/sqlalchemy/blob/master/lib/sqlalchemy/sql/util.py#L420