Bad tzinfo_tz values in production databases

[atruskie]

Due to a historical mistake we used to store different formats of timezone identifier (a 'friendly' version and sometimes the tzinfo database version). This was partially rectified by #270 but the approach there was to resolve the value to a consistent format whenever it was pulled.

Only after a save was the updated value persisted.

Unfortunately, we're now using the tzinfo_tz column in queries. Postgres itself recognizes the tzinfo identifiers but not the so called 'friendly' Rails identifiers.

We need to proactively clean out the old values in our production databases.