DeviceInfo refactor, do not crash on missing fields

[rytilahti]

• Move the implementation to its own module (from Add model autodetection #1038)
• Add ip_address and token properties
• Add tests

Fixes #1082

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 84.37500% with 5 lines in your changes missing coverage. Please review.

Project coverage is 75.47%. Comparing base (a377d76) to head (a275c9d).
Report is 376 commits behind head on master.

Files	Patch %	Lines
miio/deviceinfo.py	83.87%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1083      +/-   ##
==========================================
+ Coverage   75.40%   75.47%   +0.07%     
==========================================
  Files          73       74       +1     
  Lines        8367     8367              
  Branches      745      741       -4     
==========================================
+ Hits         6309     6315       +6     
+ Misses       1874     1870       -4     
+ Partials      184      182       -2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[rytilahti]

Merging as this should not break anything.