Added sentence casing description, changed description title casing a bit.
Merge remote-tracking branch 'upstream/master'
Merge branch 'master' of https://github.com/citation-style-language/documentation

Conflicts:
	specification.txt
Rough text to start of a manual on extensions to CSL available in
citeproc-js.
Graphics files and grinder for citeproc-js variants manual.
Updates to citeproc-js variants manual, plus CSS file.
Add entry for subsequent-author-substitute-rule.
Add note on locator-date variable.
Add notes on "locator-revision" variable, "supplement" term and variable, and "periodical" type.
Change note to reflect new partial-each and partial-first option values.
Flag adoption of subsequent-author-substitute-rule, set a warning on the section about multiple-element cs:number, and add a working note on courts, institutions, and parallel cites.
Merge branch 'master' of https://github.com/fbennett/documentation
Checkin some long-standing changes