MDLSITE-2139 Convert to 2.x filter.

Note this commit only introduces the minimum changes required
to convert the filter to 2.x. It does not include any cleanup
nor reformat. Just the raw/plain changes. Next commit will introduce
the unit tests covering current behavior and then other changes
will land.
Merge pull request #1 from stronk7/MDLSITE-2139

MDLSITE-2139 Convert to 2.x filter.