Added featured modules back into JP homepage

Featured modules section allows us to highlight some of the benefits of
Jetpack without jumping straight to a module listing.
Merge pull request #487 from Automattic/ui-tweaks-dave

Added featured modules back into JP homepage
Merge pull request #488 from Automattic/ui-tweaks-dave

Real-time module search
Real-time module search

No reason to force them to hit enter for the search to start filtering
results.
Fixed left nav & smoother mobile scrolling

- Made main wp-admin left nav fixed again
- Also resolved jerky scrolling in iOS

The one downside is that the little marker arrow in the “Jetpack” menu
item in the left nav is white which doesn’t look as good against the
green header area on the right.  It’s not too distracting though, and
is better than changing up the left nav so that it’s absolutely
positioned just on the JP admin pages.
Merge pull request #489 from Automattic/ui-tweaks-dave

Fixed left nav & smoother mobile scrolling
Tidy up how we concatenate host and path.

props @westi

Merges r96399-wpcom.
Merges r96400-wpcom.
REST API: versioning support for REST API endpoint

Props @jonathansadowski @jkudish

Merges r96274-wpcom.
Merges r96288-wpcom.
Merges r96289-wpcom.
Merge pull request #490 from Automattic/wpcom-merge-april-23-george

Merge a couple changes in from wpcom
Infinite Scroll: ensure click handler is removed when IS is rendering the button (default behaviour)

Since the removal is within a click handler, `this` is no longer the proper scope for our needs. As a result, the "load more" button isn't removed and multiple copies will be present on the page. Introduced in r95922.

See #28321-z.

Merges r96156-wpcom.
Infinite Scroll: bump up the default footer width to accommodate longer footer links.

See http://[private link] and r96337.

Merges r96380-wpcom.
Google+ Authorship

Add an option to still enable G+ but hide from display (still adds link attribute to header, etc).

See https://[private link] requested by matt.

Merges r96140-wpcom.
Sharing Buttons

Update size of the smart pinterest button so its not stretched.

Merges r96128-wpcom.
Sharedaddy: Fix oval skew in admin interface for custom buttons with the round option picked. Also allow color icons instead of grasycale, for custom buttons.

Merges r96388-wpcom.
Sharing Buttons

Remove the pin count from the smart button preview. We don't support it anymore.

Merges r96127-wpcom.
Optimize images

Merges r96181-wpcom.
Props wpcom user @optimizerbot.
Widget Customizer: support Widget Visibility (Widget Conditionals)

See #6513.

Merges r96370-wpcom.
Pinking shears

Merges r96371-wpcom.
Merge pull request #492 from Automattic/wpcom-merge-apr23

Wpcom merge apr23
Added jetpack.disconnectBlog XMLRPC method which will allow an authenticated user to disconnect a blog from a wordpress.com account