Added new fields to trackpoints for data from GPS in realtime mode.

Added new fields to trackpoints for data from GPS in realtime mode.

- Speed, course, fix mode and number of satellites are now stored in trackpoint
  when received from GPS in realtime mode.

- There should be no backward compatibility problem. FIles saved by earlier
  version of viking can still be used.

- New data from files saved by viking from this change onward won't be
  recognised by earlier version of viking and will generate (lots of) warnings
  when read.

Signed-off-by: Quy Tonthat <qtonthat@gmail.com>