Add argument to TruncateNewCalendarStatements

[tisseo-deploy]

Summary:

GTFS Transformer: Add arguments to TruncateNewCalendarStatements in order to customize the truncating interval in days, months, or years.

Expected behavior:

The two arguments are calendar_field (day, month, or years) and calendar_amount.
Add the amount to the date, but avoid using Calendar.roll as it can result in strange behavior at the end of the year or end of the month, depending on the field argument.
Don't alter the default behavior (1 month)

[tisseo-deploy]

We will submit a pull request shortly if the team approves.

[tisseo-deploy]

Done: PR #240