HgVertex cleanup/speedup; LABEL_INVALID_CHAR fixes

[yakra]

• closesvertex-related cleanup yakra/DataProcessing#107
  • 3f938cb cleans up vertex iteration. Dict keys are Waypoint objects rather than vertex labels now, and can be used for the HIDDEN_JUNCTION datacheck rather than the vestigial first_waypoint variable.
  • A longstanding comment notes that we can remove either lat & lng or first_waypoint from HGVertex, but not both. 315f834 removes first_waypoint. This option takes up about 4 MB more RAM, but the other option is slightly slower and requires minor changes to PlaceRadius.
• closesstr(HGVertex) yakra/DataProcessing#153
  • ac65bc3 constructs & stores .tmg vertex line strings only once, retrieving them to write to all 3 graph files. This saves a surprising amount of time, subgraphs down to 67.23 s from 74.77 s on lab1. Python string construction gets pretty expensive what with interning, automatic hashing, etc.
• closesUTF-8 byte order mark HighwayData#4561
  • b155944 flags LABEL_INVALID_CHAR only once per waypoint label, and notes cases caused by a UTF-8 BOM.
  • See also: UTF-8 BOM Web#630

[yakra]

Might have one more commit to add on to this.

[jteresco]

bring in?

[yakra]

Ready to bring in. I'll save that commit for later.