Cleaned up Adding Models for General Use documentation

[antoninkriz]

Minor cleanup of some mistakes in the documentation I stumbled upon when implementing a new model

[ablaom]

Looks good to me. Much appreciated.

Let me know if you need further guidance implementing your interface.

[ablaom]

@antoninkriz Do you mind rebasing your PR so as to make dev branch the target?

[codecov-commenter]

Codecov Report

Merging #1019 (9467c98) into dev (ec999a1) will not change coverage.
The diff coverage is n/a.

❗ Current head 9467c98 differs from pull request most recent head a826318. Consider uploading reports for the commit a826318 to get more accurate results

@@           Coverage Diff           @@
##              dev    #1019   +/-   ##
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  Coverage   42.85%   42.85%           
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  Files           1        1           
  Lines          28       28           
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  Hits           12       12           
  Misses         16       16           

[antoninkriz]

@ablaom Done, thank you!
The master branch was a missclick, I shoud've noticed it sooner.

[ablaom]

thanks again