Currently there is an edge-case in the turn restriction implementation,
such that routes can not be found if the target input location snaps
to a way used in a (multi) via restriction.
With the addition of snapping input locations to multiple ways, we
can now also snap to the "duplicate" edges created for the restriction graph,
thereby fixing the problem.
This is achieved by adding the duplicate restriction edges to the
geospatial search RTree.
This does open up the possibility of multiple paths representing exactly
the same route - one using the original edge as a source, the other
using the duplicate restriction graph edge as source. This is fine,
as both edges are represented by the same geometry, so will generate
the same result.
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