Document all options and their forms in one table

[mpeterv]

Right now options for CLI, config, and inline comments are documented separately in different doc pages. Some options can be used in all three scopes, some can't.

It would be nice to have a single table containing all options, including name, meaning, and usage examples for the three scopes when applicable, like this:

Option	Description	CLI usage	Usage in config	Inline usage
ignore	Do not report warnings matching given patterns	--ignore <pattern> [<pattern] ...	ignore = {...}; files[glob].ignore = {...}	luacheck: ignore ...; luacheck: ignore without arguments ignores all warnings

sphinx-rtd-theme does not seem to handle wide tables very well, may need to switch to a different Sphinx template and maybe host the docs on GIthub Pages again.