First draft of getting started docs for UI
Porting old UI Theming docs from MediaWiki - See #187 & #230
How to write a theme - See #187
Merging #220 into ui-docs branch - @redwolves Issue #209: Migrated Widget Factory Docs

Conflicts:
	order.yml
	page/jquery-ui.md
Fix order.yml to properly reference jQuery UI nested chapters
Update jQuery UI download builder screenshot to reflect new site design
Add some basic summary information to the Widget Factory landing page, other minor edits to imported jQuery UI content
Update CONTRIBUTING.md to reference contribute.jquery.org docs instead of duplicating instructions. Also revise the section on how to use GitHub UI for creating new content
Update license to MIT and fix copy to reflect MIT usage
Merge branch 'ui-docs'