police etc landuses

This provides rendering for areas of amenity={police|prison} and landuse=religious, and closes

https://trac.openstreetmap.org/ticket/5197
https://trac.openstreetmap.org/ticket/3622
https://trac.openstreetmap.org/ticket/2512

Prison was apparently implemented in xml and did not make it to carto. The others are new.

The design for police adopts the diagonal hatching style we have for military areas/barracks, just in a neutral grey that blends with residential landuse. Prison does vertical hatching, as in the original implementation. Both icons are powers of two and allow global alignment. Landuse religious darkens residential colour by 8% and is in saturation between this and a place_of_worship.
![po](https://cloud.githubusercontent.com/assets/8266355/3714299/78c88a5c-15a0-11e4-80a4-acc21008b339.png)
![pr](https://cloud.githubusercontent.com/assets/8266355/3714300/78cc44d0-15a0-11e4-87d1-41389387fb5f.png)
![rl](https://cloud.githubusercontent.com/assets/8266355/3714301/78cfd852-15a0-11e4-86c2-cf20f0c7210a.png)