hash tables for waypoint labels?

[yakra]

#230 (comment) got me thinking...

We already use a hash table for looking up region/highway combos.
How about a couple hash tables for each route, for looking up primary labels & AltLabels?

[yakra]

This, like #272, would also mean we're no longer counting point_indices, meaning no error in the user log when a duplicate label is used in a .list line, unless a solution to #275 is implemented.

[yakra]

Hash tables can be used in place of sets for the DUPLICATE_LABEL datacheck.
Conversion will be more straightforward in C++, where most datachecks have already been folded into the Reading waypoints for all routes process.

[yakra]

• clear pri_label_hash and alt_label_hash after .list processing to save RAM.
  Takes up an estimated 63.9MB, C++, 79.9MB Python