Fix for #134 - be explicit about the timezone when inserting detections ...

...and events, otherwise the database's configured timezone is assumed.

Note: this PR does not attempt to fix any of the duplicates which currently exist.  It's a bit of effort to do this, I think much better to implement [validate detections on the fly](https://github.com/aodn/aatams/issues/72) which will fix this problem implicitly.