Python API: Move to asyncio, async, await, etc.

[mlyle]

Since we're on python 3, use the new syntactic sugar, sugar.

[tracernz]

And use exceptions more for error handling? :stuck_out_tongue:

[mlyle]

Hmmmm. This is looking like a pain.

Using yield from looks like it requires way too much of a complexity/performance tax for the factoring improvements it can provide in uavtalk.

It looks like moving to an event loop with asyncio would provide some small factoring improvements.