This is a branch under development to incorporate via way restrictions, currently with the 'no_' case with a 3-member restriction (from, via, to).

This will work as follows:

• Read in restrictions if they are a "no_*" restriction on three ways: a->b->c
• Write out the turn restrictions to the .restrictions file along with the regular restrictions in a special format (documented in the code)
• Parse in restrictions and during the edge based graph building phase
• Create extra edge based nodes for the middle way (the via), which essentially retain the state of coming from the "from" way.

Concretely, let's say we have three ways in the restriction: a->b->c (a is the from, b is the via, c is the to). We create a new edge based node (b') and take all of the outgoing edge_based_edges of b and duplicate them so that b' also has those outgoing edges. Next we delete the edge_based_edge connecting a to b and create an identically weighted one from a to b'. Finally we delete the edge from b' to c.

I'll be adding commits to this branch, but would love feedback as I continue development.

@TheMarex @danpat