Only translate default tags

We translate only tags we know since possible
translations of custom tags (provided by the user)
may be out of context and therefore wrong.

Signed-off-by: Maximilian Güntner <maximilian.guentner@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Fix trip summary line in dive list

Two errors fixed.

- With no location set, the summary line would start with a ','.
- When auto creating a trip for a manually added dive or when editing the
  dates of dives in a trip, the timestamp for the trip was not updated
  after editing the dive.

Fixes #293

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>