Moved flush() logice into Push.flush()
Moved selectedDevice global into Model.gtSelectedDevice().
Refactored all usages.
Removed device from global scope, refactored into CursorDeviceProxy.
Renamed Transport to TransportProxy.
Removed the global variable push from files
- still exists in the control file only to be used
  in init(), flush(), exit()
Merge pull request #73 from teotigraphix/master

Refactoring out global variables from main control script