Added a new column to the tracking parameter panel ReferencePositionEnd. Adjusted the tracking algorithms accordingly.

Added first version of the new backward tracking method. It is now possible to use interpolation methods as well.

Bugfix, the date and toa values have been duplicated after interpolation for unknown reason. This has been removed.

The save feature for offsets in trajectory does work now. It was
already implemented, but did not work because of the variable name.

/ Float offsets are now integrated into the table
/ Options to either use manual or calculated offset (last one not done yet)
/ Added begin and end offset for soundsources to enable input of drift (drift not implemented yet)
/ Updated GUI of track parameter

+ Added checkbox to enable mercator projection
+ Added checkbox to show/hide position dates
+ Extended position dates by rafos day
+ Added colors for trajectories
/ Improved soundvelocity caluclation
+ Added clock error calculation