Add support for the Beuchat Voyager 2G.
Another gitignore update.

Signed-off-by: Cristian Ionescu-Idbohrn <cristian.ionescu-idbohrn@axis.com>
Disable the gas mixes in gauge mode.
Improve the warning and error messages.
Remove the percentage variable.

There is already another variable for the O2 percentage, so re-use that
one instead.
Fix the length of the Suunto DX gas change event.

The Suunto DX uses 5 bytes for the 0x06 gas change event.
Merge branch 'dx'
Apply the gas mode immediately.

Because the gas mode takes precedence over the individual gas mix
definitions, we can simplify the code by taking the gas mode into
account immediately when parsing the gas mixes.
Cache the initial gas mix.

The gas mode should not only be taken into account for parsing the gas
mix definitions, but also for the initial gas mix. Because the logic
needs to be kept in sync, it's convenient to have all related code in a
single place, and cache the value.
Ignore disabled gas mixes.

For the older models, gas mixes are disabled by setting their oxygen
percentage byte to 0x00 or 0xFF. Trying to parse such a byte as a valid
percentage results in an invalid gas mix.

Because the device doesn't allow you to enable a gas mix if the previous
gas mix has already been disabled, we can simply stop parsing the gas
mixes once the first disabled gas mix has been found.
Merge branch 'gasmix'
Fix the temperature for the Sherwood Wisdom 2.

The sign bit should be reversed for this model.