Grab a bit more info from UDDF import

otu and po2 are now grabbed. The po2 value comes from setpo2 tag. Also
divecomputerid is constructed from the generator information.

Signed-off-by: Miika Turkia <miika.turkia@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>