Missing or wrong defaultValues for StopTimes

[hbruch]

Summary:
Various fields in StopTimes.java define no or wrong defaultValues in the CSVField annotation, e.g. for departureBuffer -1 is set as default, but the initialized value is 0. For all fields initialized with MISSING_VALUE, like e.g. endServiceAreaRadius, their string equivalent of -999 should be the defaultValue.

As a result, these fields are written though all values a missing.

Steps to reproduce:
Transform a GTFS feed and open StopTimes.txt. It contains e.g. the column departureBuffer with value 0, though it was unchanged and did not exist in the original feed.

Expected behavior:
No new columns are added without explicitly setting values for these.

Observed behavior:

What happened instead? Describe your issue in detail here.

Platform:
N.A.