docs($htaccess): Fix some urls not working

- Fixing index pages for directories (e.g., .com/api/)
- Fixing index pages for branches and tags (e.g., .com/branch/, .com/tag/)
- Fixing loss of ability to look at tag-specific docs (e.g., .com/tag/3.9.0/)

[skip ci]
fix(dnd.js): fixes #1100 DnD TypeError in Safari
chore(*): prepare for 4.2.1 release #1100
chore(README.md): prepare for 4.2.1 release #1100

[skip ci]
docs($s3) typo

[skip ci]
docs(api/options-ui.jmd): Wrong types for element/listElement options

 [skip ci]
Merge branch 'master' into develop

Conflicts:
	README.md
	bower.json
	client/js/version.js
	fineuploader.jquery.json
	package.json