Integrate loading of uemis SDA files into the regular xml parsing

Integrate loading of uemis SDA files into the regular xml parsing

There are a few interesting issues with this:

- this requires a change to the SDA file format; thankfully I control that
  format, too (the default files are not valid XML files)
- once again, the fact that adding samples can change the dive pointer
  messes with me - I decided to change the interface of ALL of the
  XXX_dive_match functions to take a struct dive**
  I know this is not ideal as all the other functions don't need that -
  but I would have hated the inconsistency
- there is the issue that we now overload two _different_ uemis formats in
  the same function - that's certainly a potential point of confusion
- a minor detail is the problem that the SDA format is kinda odd to parse
  and that we trigger on the duration field by it being the only float.
  Yeah, that's not ideal - but again, I control the format, so I _know_
  this is true.

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