Allow penalties for arbitrary nodes

Currently penalties are limited to traffic lights. That is overly restrictive as we could also use it for traffic calming and mini-roundabouts are mentioned in this PR https://github.com/Project-OSRM/osrm-backend/pull/534.

Brain dump on how to do this:

• Replace bool ExtractionNode::traffic_lights with short ExtractionNode::penalty
• Adapt graph_loader.cpp to load nodes with penalty > 0 in a separate array
• Adapt m_traffic_lights in EdgeBasedGraphFactory