Default dive number on manual CSV import

If manual CSV import does not have any dive number, give a default one
so that the dives get import and not silently ignored.

Signed-off-by: Miika Turkia <miika.turkia@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Tooltips for some of the manual CSV import fields

Date and duration formats are not necessarily self explanatory so adding
tooltips to explain the expected format.

Signed-off-by: Miika Turkia <miika.turkia@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
CCR dive logs: git I/O

This patch privides for writing CCR dive log parameters to a git
repository and for reading the data back from a git repository.
This involves writing and reading the following members of the
structures of sample:
  o2sensor[3]
  o2cylinderpressure
and dc->no_o2sensors.

Signed-off-by: willem ferguson <willemferguson@zoology.up.ac.za>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Let's not store more or less random data

The backend needs to convert the firmware and serial information into a
sane string - Subsurface shouldn't try to do this by itself.

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