Extend zoom calculation to nxm tilesets

Previously tile sets generated for the live map where fixed to max 2x2 tiles. In order to enhance the flexibility of the live-map algorithms, now the generation of more fine-grained tile sets or even a lower bound for the zoom level to use is supported.

This is an internal feature @mucek4 asked for in order to enhance the live-map parsing.

So after scrutinizing and discussion it is up to him whether he wants to include it in his work and merge then or independently already before.