fix ab4s:import update booking activation/deactivation.  WIP #1
dont deactivate all bookings in the case of missing import file or failed import
[ab4s:import] remove unnecessary debug message
[ab4s:import] coding style formatting
[ab4s:import] clearify code comment
Fixes #6 : ab4s:import update does not actually update booking information
implement booking update mechanism
[ab4s:import] on update, make sure an existing booking is found before proceeding
[ab4s:import] do not update existing bookings when "update" command is not used
[ab4s:import] improve existing destination detection on moving folder