Enable shadowmaps on street lights

[ElmarJ]

Currently, street lights don't render shadow maps, meaning that the light reaches through buildings. It is not a big problem (you have to look well to see it), but enabling shadow maps does definitely look better (also because the lamp post itself draws a shadow), see screenshot below.

It is easy to enable in the prefab (update shadowmaps on demand, with a relatively low resolution - e.g. 128 - looks very good already), but before enabling I have to better study the performance cost.