Returned geometry

Fix  Issue #202 

This PR includes:

- The possibility to define a parameter to tell which geometry should be returned
- The geometry being queried is always 'the_geom'
- Some cleanup
- The addition of the Lubis model (and DB connection)
- A minimal mako template for Lubis
- A test to make sure Polygons are returned when querying ch.swisstopo.lubis-luftbilder

To be implemented in a separate PR I am preparing:
- timesupport in identify (using timeInstant)
- refactoring of zeitreihen model using class mixin (same approach with Lubis)