Use our types in interpolate_transition

Signed-off-by: Henrik Brautaset Aronsen <subsurface@henrik.synth.no>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Pull latest translations from Transifex

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Getting read for Beta 2

Tiny updates to Relnotes and README, include the latest formatted manual,
change the version in the project file

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
get_gas_at_time needs to always give us a valid gas

Before this function was changed it was really supposed to just change a
gas that was passed in in case there was an event that changed the mix -
but with the new name the caller will assume that they get a valid gasmix.
And promptly we had one caller that didn't initialize gas to be based on
the first cylinder before calling get_gas_at_time().

Instead of adding yet one more spot that knows about the oddity of the old
API I simply changed get_gas_at_time() to do what it name appears to imply
and fixed the other callers not to bother to initialize the gasmix.

Fixes #647

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