Clarify the meaning of the values in the stats tab

Extend the tooltips to be shown both on the labels and the values and add
tooltips for all min/avg/max elements.

To avoid confusion when only one dive is selected, no longer show min SAC
or max SAC or min duration or max duration.

Fixes #694

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Latest strings and translations

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