Add TMSTileFilter filter

This extends the InBBOXFilter and adds support for specifying the bbox based on a TMS tile address. This is useful for generating GeoJSON tiles for use in web mapping libraries such as https://github.com/glenrobertson/leaflet-tilelayer-geojson 
better to write:

   import math

and then:

    math.pi, math.pow, etc

or:

    from math import pow, pi ....