Sharing: Check if label value is set before to display it

For more details, check the original trac ticket:
http://plugins.trac.wordpress.org/ticket/1974
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
Jetpack: Sharing: Consolidating 'Share this' message to one location
Jetpack: Sharing: Adding sanitization function
Jetpack: Sharing: Added default label for sharing on the front end
Module Related Posts: Cleanup CSS Selectors

Make CSS selectors more consistant and more specific so that it's less
likely to be overridden.
Revert "Jetpack: Sharing: Added default label for sharing on the front end"

This reverts commit 95e05064afe5b2498cd3d5c12c22d05aafa7c116.
Merge pull request #18 from jeherve/1974-trac

Sharing: Check if label value is set before to display it
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
Module Related Posts: Add a default context to preserve the balance
Merge pull request #307 from xyu/module-related-posts-default-context

Module Related Posts: Add a default context to preserve the balance
Merge pull request #305 from xyu/module-related-posts-cleanup-selectors

Module Related Posts: Cleanup CSS Selectors
Module Related Posts: IE9 Compat Fix

IE9 does not support `history.replaceState()` which breaks rendering of the
related posts section. Abort trying to cleaning up the URL if we cannot
rewrite state. (Sadly this leaves cruft on the URL of older browsers.)
Merge pull request #310 from xyu/module-related-posts-url-cleanup-ie9

Module Related Posts: IE9 Compat Fix
SSO: Finish nerfing the login nuker.

When @blobaugh commented out the option, he never stopped the code that
the option kicks off, so any beta testers that had it flipped on
couldn’t deactivate it, and have had a feature they shouldn’t on
production.  This should do that.
Add changelog for 2.9.1