turn restrictions on/off in lua profiles

implements a simple way to turn restrictions on/off in the lua profile, by setting a global:

```
use_turn_restrictions   = true       -- false to disable turn restrictions
````

this is useful in foot and bike profiles, when you don't want to restrict any turns.

based on earlier pull request from @lonvia: https://github.com/DennisOSRM/Project-OSRM/pull/479

implements it in the pbfparser only. should the xmlparser be supported too?