Don't mask the filter built-in

There was an argument to a function called 'filter'. 'filter' is a
python built-in, so that name shouldn't be reassigned
to something else since that will mask the built-in which can be
confusing and problematic when someone wants to use the built-in.

Also, changed the name of the sql.Base member to filter_query for
the same reason.

Change-Id: I8eb13c73bd8cf0f31e08951bc0fcaf49abd49ef1
Merge "Don't mask the filter built-in"