Feature/257 input controller active deactivate

see https://github.com/OpenROV/openrov-software/issues/257


## Activating / Deactivating

Rather than registering and unregistering, you can register a command as inactive, this way, it is registered, but not yet active.
All you need to do is to activate it via a message later.

    this.cockpit.emit('inputController.register',
      {
        name: "example.keyBoardMapping",
        description: "Example for keymapping.",
        defaults: { keyboard: 'alt+0', gamepad: 'X' },
        active: false, // <-- DEACTIVATED
        down: function() { console.log('0 down'); },
        up: function() { console.log('0 up'); }
      });

To activate:

      rov.cockpit.emit('inputController.activate', 'example.keyBoardMapping');

To deactivate:

      rov.cockpit.emit('inputController.deactivate', 'example.keyBoardMapping');

Both, activate and deactivate allow to use arrays too:

      rov.cockpit.emit('inputController.activate', ['example.keyBoardMapping', 'example.keyBoardMapping2' ]);
      rov.cockpit.emit('inputController.deactivate', ['example.keyBoardMapping', 'example.keyBoardMapping2' ]);

See the Tankcontrol plugin for a working example.
Typo. Will fix.