add route_pattern table (need a current_route_pattern table too?)

[fpurcell]

calculate all the patterns belonging to a route into route_pattern

further, do we need a current_route_pattern? alt, do we really need a current_pattern table, ala #45 ?

I think we need current_route_pattern, since we currently have route_id 100 (which doesn't change over time), but the list of patterns for route_id 100 do change over time.

And with a current_route_pattern, do we need a current_pattern table?