Tile Server policy and agreement

[josefkreitmayer]

We need to forward the policy of our tile-server providers to SSEDAS, and have an agreement about how to handle possible overusage. Basically that is a voucher for us not to be responsible for such case, and to what extent we take responsibility to bridge communication.

Tile server policies from
OSM tiles: http://wiki.openstreetmap.org/wiki/Tile_usage_policy

@species