pgr_dijkstraVia that supports points

[robe2]

This is proposal for a new function.

pgr_dijkstraVia as of pgRouting 2.4 only supports physical nodes. As a result, if you want to force a certain order of visiting and your points don't coincide with nodes in your network, you need to use pgr_trspViaEdges even if you have no turn restrictions.

Would be nice if there is a pgr_dijkstraViaWithPoints or and overloaded pgr_dijkstraVia (similar to pgr_dijkstraWithPoints), that supports including virtual nodes.