Multiple cylinder support for JDiveLog import

Multiple cylinder support for JDiveLog import

Support for multiple cylinders and gas change events when Importing
JDiveLog logs to Subsurface. This is tested with manually crafted data
and not real data (originating from dive computer).

NOTE: Subsurface does not handle importing multiple cylinders
correctly but imports only the first cylinder. However, manually
converting data to a file and opening that in Subsurface works
correctly.
 (xsltproc jdivelog2subsurface.xslt jdivelog-gas.jlb > gas.xml)

Some minor tweaking on importing JDiveLog specific fields to notes
fields in Subsurface is also included.

Signed-off-by: Miika Turkia <miika.turkia@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>