Add option to completely deactivate FLY events

[pfink]

It would be nice to add the possibility of completely deactivating FLY events so that the user cannot mistakenly enter the "fly over" mode which consumes much battery and (in my tests) also seems to make the recognition of other events (especially SWIPE_UP and SWIPE_DOWN) more inaccurate. I already had the case that visitors mistakenly entered the "fly over" mode which caused a little bit of confusion ("Why is there suddenly a LED blinking?", "Now swiping UP/DOWN does not really work anymore", ...).

I think for many use cases the "fly over" mode is not really necessary (e.g. if the Nuimo is used as a wall switch) and for those, it would be cool to have the option completely deactivating it. So I'd suggest:

• default behavior after connecting: User can activate FLY over mode by holding the top surface for 2 seconds (as always)
• behavior if FLY over mode was explicitly deactivated via a method within this library: User cannot activate FLY mode at all.

Of course even more sophisticated would be if the developer has complete control if and when "fly over" mode is activated.