style: remove trailing comma
remove __all__ and prefix clib var with underscore

Not need to define __all__ if we mark 'private' vars with an underscore.
move of spacemouse_list closer to DeviceList class
use the update keyword in DeviceList class

This implementation use 'update' as a keyword only arg in a way that is
compatible with both python 2 and 3.
change register events design

* Delete reg_events.py and consolidate all event types to event.py.
* Rename SpaceMouseEventMotion to SpaceMouseMotionEvent, also for
button and led.
* Move from convoluted dict based design for register events to class
design, which allows easy manipulation.
* Register events now work basicly like calling a function with the
event as argument.
* Add simple led register events.
* Register module now uses this simple call convention for register
events.
no need to keep dict merge utility function
use event module and default update=True for DeviceList