Fix versionadded directives

Use 0.14.0 instead of 0.14, for consistency.
Change to yaml.dump
Merge pull request #8231 from pass-by-value/yaml_dump_change

Change to yaml.dump
Clarify grains precedence

Resolves #8107.
There won't be a Salt `0.20.x`.
Skip known state internal keys.
Properly handle requirements files not found.

If a requirements file is not found, the `pip` salt module does not even execute the `cmd` call, so, there's not `retcode`, `stdout` or `stderr`.
There won't be a Salt `0.19.0`.
Ignore known salt internal arguments.
Double to single quotes.
Add some more known state internal keywords.