extra data display

[Dirk Hohndel]

I had planned to do this as early as the early 3.x series and then again
for every release in the Qt days and never got around to it. It's still
rather rough (and the UI needs some love) but I wanted to make sure that
this makes it into 4.3 this time around.

We now can get unstructured data from a dive computer in form of key/value
pairs and store them with the data and show them in Subsurface. This will
be extremely useful for data that doesn't easily fit into cleanly
abstracted categories. Things like "battery value after a dive". Some dive
computers give you a voltage, some give you some magic number (and of
course many give you nothing). Things like actual version strings. The
deco algorithm and parameters used. No fly time. Etc.

Whatever we can extract from the dive computer and that is semi useful.

Please take a look at the implementation and especially the visualization.

I also pushed a bunch of random other changes from the mailing list. Daily
Windows binaries are being posted as we speak.

/D