Add support for discovering new devices via broadcast of their first heartbeat

[bdraco]

• Adds set_discovery_callback which will immediately discover devices when they boot up when push updates are active.
  Devices broadcast a firstBeat udp packet on boot with their mac address which allows us to discover new devices, and update the ip address we have for the device to avoid having to wait for the next discovery.

• Adds white channels and white to color ratio from bulb config. The data described in #77 seems to be a lot more generic and its actually the number of white channels and white to color ratio. Closes #77

• Various refactoring and tests to increase test coverage

• Remove connect_on_init as it did blocking I/O which would stall the event loop

[bdraco]

The descriptions may be too specific as I think the models are a bit more generic

[codecov-commenter]

Codecov Report

Merging #111 (b788440) into master (772566f) will increase coverage by 44.49%. The diff coverage is 82.45%.

@@             Coverage Diff             @@
##           master     #111       +/-   ##
===========================================
+ Coverage   29.59%   74.08%   +44.49%     
===========================================
  Files          13       12        -1     
  Lines         821      741       -80     
===========================================
+ Hits          243      549      +306     
+ Misses        578      192      -386     

Impacted Files	Coverage Δ
pywizlight/push_manager.py	26.31% <37.50%> (-0.20%)	:arrow_down:
pywizlight/bulb.py	75.88% <81.81%> (+50.88%)	:arrow_up:
pywizlight/utils.py	89.18% <82.60%> (+54.18%)	:arrow_up:
pywizlight/models.py	92.30% <92.30%> (ø)
pywizlight/bulblibrary.py	91.66% <100.00%> (+26.44%)	:arrow_up:
pywizlight/discovery.py	77.96% <100.00%> (+36.53%)	:arrow_up:
pywizlight/rgbcw.py	72.91% <100.00%> (+55.20%)	:arrow_up:
pywizlight/scenes.py	100.00% <100.00%> (+57.14%)	:arrow_up:
pywizlight/vec.py	89.28% <100.00%> (+28.57%)	:arrow_up:
pywizlight/cli.py
... and 9 more

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[bdraco]

So wcr is White to Color Ratio, and nowc is number of white channels.

I don't think this actually gives enough info to identify the device

[sbidy]

So wcr is White to Color Ratio, and nowc is number of white channels.

I don't think this actually gives enough info to identify the device

Yes, thats true. I don't see a chance to have such a generic approach with the info we got from the UDP interface. Maybe we got a new property for a possible detection of the physical shape of the bulb/stripe/etc..

Thank you for jumping in and having a second look into that.