Rename line-length to line-width

[MichaReiser]

Rename the line-length setting to line-width. Update the documentation to mention that is also used for the formatter and that it is the line width and not length.

Support line-length for an interim period. Warn when users use line-length.

Note: We may want to consider adding an alias support to our option macro.

Maybe: Update the lint and remove/replace the characters in the message because it isn't measuring characters.