Validator: parity with Google transitfeed feedvalidator

[landonreed]

I think it would be useful to review the list of validation errors and warnings thrown by the Google transitfeed validator to ensure we're not missing anything glaring in gtfs-lib. I'm not sure this has been done (at least on the RDBMS code path) and I would like to say with confidence that gtfs-lib is performing every check made by this peer tool.

Edit:
Here's a running list of some checks I've discovered that we're not running (with the corresponding error type in NewGTFSErrorType or commit it was added):

• check stop names/descriptions (Validate stop names and trip headsigns #169)
• check trip names/headsigns (Validate stop names and trip headsigns #169)
• check for overlapping frequency periods 2437438
• check for nonzero transfer_duration for fares not allowing transfers 60124ee
• shape validation (see Better shape validation #130)
  • shape contains points (actually I think this is covered by our referential integrity checks)
  • shape_dist_traveled is increasing
  • shape unused
• better message for TIME_ZONE_FORMAT (not a feature disparity, but something I noticed while auditing the validators) d0f849c

  gtfs-lib/src/main/java/com/conveyal/gtfs/error/NewGTFSErrorType.java

  Line 37 in 76d89e9

  TIME_ZONE_FORMAT(Priority.MEDIUM, "Time zone format should be X."),

• check non-utf, encoding issues, or line endings
• "This stop time has a pickup_type and drop_off_type of 1, indicating that riders can't get on or off here. Since it doesn't define a timepoint either, this entry serves no purpose and should be excluded from the trip." c1b3b23
• service not active on any days of the week (SERVICE_NEVER_ACTIVE)
• feed has no effective service dates (NO_SERVICE)
• stops in close proximity (we are checking for stops in the exact same location with DUPLICATE_STOP)