Revised Timezone handling

BC Break!!!

This release switches to storing recording times as ISO date-time strings with inbuilt timezone - previously the timezone was lost by Django's internal handling on most storage backends.

We also display all times within the app as local - as the Guano spec says:

… Local time is overwhelmingly more important when it comes to bat echolocation data than is absolute UTC time …

As we can't work out the lost timezone from the existing stored UTC value, we can't populate the iso date field automatically, so you'll need to update any previously imported data using importaudiofile -f. Until you do that, all recordings will show as untimed.

Initial documented release

0.4.0