Refactor SQL filtering - Githubissues

This PR:

put methods into their own files and put under direct unit test
fixes a bug in the "envelope-intersects" operation. The old code was checking for an intersection of the feature envelope against the query geometry. However, research indicates that the Esri envelope-intersects operation should check that an "Envelope of Query Geometry Intersects Envelope of Target Geometry" (see here).
adds support for the != operator in the hashed OBJECTID comparison.

koopjs / winnow