QuickPress: Disable autocomplete for content, enable "Save Draft" button on load.

props morganestes, michalzuber.
fixes #27760.
Built from https://develop.svn.wordpress.org/trunk@29323


git-svn-id: http://core.svn.wordpress.org/trunk@29104 1a063a9b-81f0-0310-95a4-ce76da25c4cd