Change how the local time is decided from a GMT timestamp.
This is quite a major change. It brings two great fixes.
1. We should no longer see the problem when using dateStringToTimestamp() were you want a timestamp for 2014/04/30 00:00:00 but you get one for 2014/04/29 23:00:00.
2. Previously when a time is formatted from a GMT timestamp to a local time string the current GMT offset was added to the timestamp.
This meant that when DST happened the times would either jump back or jump forward one hour. This is actually solved now.