Modify system shutdown command.

New flag to shutdown at a given time. Refs #7833.
fixed typo in rpm module documentation
Merge pull request #8228 from sijis/docs_modules_rpm

fixed typo in rpm module documentation
Improve documentation regarding nested dict YAML indentation
Typo fix
Updating capitalization
Merge pull request #8229 from techhat/typo

Typo fixes
Move image out of the theme folder to quiet sphinx warning
Update the Transifex translations sources.
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.