Fix tracking parameters gui

Following the updates of Traits and TraitsUI by Enthought, some old inconsistency has been revealed  in our connection between the GUI and the parameter files. This bug popped up in one of the messages of Hristo that tried to install a newer version of ETS and failed. Then, we managed to install it somehow with the older version of traits and thought it is the installation problem. 

There are few indentation fixes but the main change is here: 
https://github.com/alexlib/openptv-python/compare/OpenPTV:master...alexlib:fix_tracking_parameters_GUI?expand=1#diff-abb4cb05544c8674d056ef62a1004d76R153

The translation from integer to Bool and back that worked before under the hood now failed. The way Tracking Handler is now written is consistent with the other Handlers.