This adds support for DC reported ceiling when importing the Shearwater
Desktop database. Both AI and non-AI versions are tested, but not all
possible paths. For non-AI the DC reported ceiling was from
firstStopDepth and for the AI version it was from the decoCeiling field.
I do not currently know when each of these fields are used, but at least
this works on my test data.
Signed-off-by: Miika Turkia <miika.turkia@gmail.com>