Configure UTC log time-stamps.

Change the Django instance logging configuration to use UTC time-stamp rather than the local time.

@eox-cs1 wrote:
> Ensure that all timestamps used eg. in log-files, DB-entires, etc. are in the same time-zone (preferably > UTC). It is rather confusing to always consider time-zome or daylight-savings-time when
> searching/comparing log- or DB entries for certain occurrances.