Adminizer intersection modes

Added "collect" and "split" modes, and fixed the "first" mode already implemented in the adminizer.

* "first" mode sets the parameter for the first admin polygon which is hit by a feature.
* "collect" mode sets a delimited set of all admin polygons which are hit by a feature.
* "split" mode splits features at admin polygon boundaries and assigns the parameters according to the polygons which are hit (either "first" or "collect")