This commit also fixes the application of the empiricalShift in the
tracking algorithm. It is now applied the same way as the offsets,
namely: TOA + -1 * empiricalShift

The soundsource combinations table now has a "use" boolean for enabling/disabling the combination during tracking.

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.

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

+ 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