Add get_liveview command to camera module

[fronzbot]

Description:

Adds liveview extraction for camera

Related issue (if applicable): fixes #167

Checklist:

• Local tests with tox run successfully PR cannot be meged unless tests pass
• Changes tested locally to ensure platform still works as intended
• Tests added to verify new code works

[codecov]

Codecov Report

Merging #289 into dev will decrease coverage by 0.17%.
The diff coverage is 33.33%.

@@            Coverage Diff             @@
##              dev     #289      +/-   ##
==========================================
- Coverage   81.73%   81.55%   -0.18%     
==========================================
  Files           8        8              
  Lines         805      808       +3     
==========================================
+ Hits          658      659       +1     
- Misses        147      149       +2     

Flag	Coverage Δ
#unittests	81.55% <33.33%> (-0.18%)	⬇️

Impacted Files	Coverage Δ
blinkpy/camera.py	81.51% <33.33%> (-1.25%)	⬇️

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[jwenz723]

Typically a blink camera is not actually streaming any video unless you go into the blink app and hit the button to activate the live stream. Does executing get_liveview() simulate the same behavior as clicking that button to activate the stream?

I've successfully invoked get_liveview() to generate an rtsps uri, but I have been unsuccessful in viewing the stream while using ffmpeg cli, vlc player, or home assistant (using the built in ffmpeg). Do you have any examples of how you are viewing the live stream?

[fronzbot]

All get_liveviee() does is call the API endpoint to retrieve a stream link. I have not tested viewing the stream yet, so don't have any working examples.