implementation of use_restrictions switch

I needed the use_restrictions setting for pedestrian routing, so I had a go at implementing it.

The setting of the use_restrictions variable in the lua profile script is checked during relation parsing and turn restriction relations are skipped if it is set to false. Works for both, XML and PBF parsing.

Currently, the variable defaults to false if not set at all. Not sure, if that breaks some unwritten assumptions. I did run the test suite and there are no additional errors.