cochran: add support for importing the exported CSV files

The Cochran Analyst software can export the basic dive information as
CSV files (comma-separated values).

Individual CSV files contain just one particular type of information:
depth, temperature or cylinder pressure, which is rather inconvenient.
However, the way subsurface works, you can just import these CSV files
all as individual dives, and then subsurface will automatically merge
the dives with the same date and time - and in the process it will also
merge all the samples.

So it turns out that we don't really need any special handling.  You can
literally just do

     subsurface <list-your-cochran-export-files-here>

and you're all done.

Of course, the CSV files really *are* pretty useless, since they don't
contain all the nice information about where the dive took place etc.
So you literally just get the dive profile.  But that's better than
getting nothing at all.

I'd love to actually be able to parse the real native Cochran Analyst
software CAN files, but in the meantime this is at least a starting
point.  And if I'm ever able to parse those nasty CAN-files, this makes
comparisons with the exports much easier.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>