Accessibility: remove unnecessary title attributes

Remove title attributes when they match the anchor text
Sharing: default $title to empty

 so it doesn't break in other functions
Sharing: revert removal of $title

$title and $text return 2 different things, so they're not duplicates
Merge branch '2006-trac' of https://github.com/jeherve/jetpack into jeherve-2006-trac

Conflicts:
	modules/widgets/gallery/templates/form.php
Merge branch 'master' of github.com:Automattic/jetpack