Update timezone setting

[GoogleCodeExporter]

For some locations, geonames does provide a timezoneId, only a GMT and DST
offset. Example: http://ws.geonames.org/timezone?lat=44.6922613&lng=-62.6571885

We should fix this so that if no timezoneId is provided, it can create a
timezone based on the offset. (But how will we create the logic for whether
to apply DST, which is generally country-specific? Maybe we'll just have to
ignore Daylight Savings Time in that case, which will kinda require us to
have a flag indicating such.)

Original issue reported on code.google.com by mkopinsky on 23 Jul 2009 at 7:21