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
Jetpack: Multisite: Adding Multisite branch to Github
Jetpack: Multisite: Removed debugging preventing get_default_modules from firing
Jetpack: Multisite: Updating tests
Merge branch 'multisite' of github.com:Automattic/jetpack into multisite
Jetpack: Multisite: Updating tests to use instance instead of instantiation
Jetpack: Multisite: Updating tests
Multisite: Activate modules when new sites are created.

If Jetpack is on a single-site installation, or is not network-activated in a multisite installation, then modules get activated automatically when the plugin is activated.

In a Multisite installation where Jetpack is network-activated, though, that doesn't happen unless we trigger it inside a wpmu_new_blog callback.
Multisite: Correct module slugs used on Network Settings screen.

Previously the module slugs were derived by running the module name through a few string manipuations, but this resulted in incorrect slugs in some cases. For instance, it resulted in "shortcodeembeds" instead of "shortcodes", and "contactform" instead of "contact-form".

Because of this, the modules failed to be activated when new sites were created because the incorrect slug was passed to activate_default_modules(), and it couldn't verify that the associated module file existed.

This commit gets the canonical slugs from get_available_modules() instead. As a result, list_modules() and its associated unit test are no longer needed.
Fix merge conflict.
Jetpack: Multisite: Adding documentation
Merge branch 'multisite' of github.com:Automattic/jetpack into multisite

Conflicts:
	tests/test_class.jetpack-network.php
Jetpack: Multisite: Moved footer html out of Jetpack_Network class and into view file
Jetpack: Multisite: Added result notification on connection event
Jetpack: Multisite: Updating tests
Jetpack: Multisite: Removing deprecated test
Jetpack: Multisite: Fixing test
Genericons: Bump to v3.0.3
Bunch of updates mostly.
- Two new icons, Dropbox and Fullscreen.
- Updates to all icons containing an exclamation mark.
- Updates to Image and Quote.
- Nicer "Share" icon.
- Bigger default Linkedin icon.
One line change to fig broken gernericon for Ben
Jetpack Monitor: Add the ability to each user to set individually if they want to receive monitor notifications.

+ Configurable at the Monitor configuration page.