Adding rough geojson controller

Current limitations
* hardcoded 'location' attribute
* Doesn't handle multiple locations, geometries or different attribute names
* Support tile params (z/x/y) in the URL but doesn't do anything with them
Add handling for tile zoom/x/y and bbox params in posts/geojson api

* Convert tile values to bounding box
* Add filtering to posts controller for bounding boxes
* Accept ?bbox= param for /posts
* Allow unlimited posts returned from /posts api controller so that
  geojson can return EVERYTHING at once
* Only handle tile values for posts collection not individual posts
Return all point attributes in GeoJSON

Checks all possible point attributes and returns them in geojson
* If just 1 value it is returned as a point
* If multiple its returned as a GeometryCollection
* If no geometries found the post is skipped
Return all point or geometry attributes in geojson

* Search both geometry and point attributes
* Use gisconverter to decode WKT to GeoJSON
Merge branch 'master' into geojson
Add GeoJSON tests

* Add api.geojson.feature for functional API tests
* Add BoundingBox and Tile class unit tests
* Add some extra test data for points and geometries
* Add test step for array count in geojson response
Update gisconverter to add getGeoArray() fn needed by geojson code
Minor changes

* Move bounding box array building to BoundingBox class
* Fix BoundingBox::toGeometry()
* Fix geometries in GeoJSON by using new toGeoArray() fn
Merge branch 'master' into geojson
Make posts search DISTINCT so we don't get duple posts for multiple locati
Make BBox sub query alias unique
Add more GeoJSON tests and allow specifying geom attribute

* Add tests for getting posts by bounding box
* Add tests for post geojson with only specified location attr
* Add support for ?geometry_attribute= param to specify geometry attribute
  for geojson
Add post id and url to GeoJSON properties, hide full resource
Merge branch 'master' into geojson
Merge pull request #73 from ushahidi/geojson

Add geojson controller for posts