Carousel: Switch slide when pressing back/forward buttons

Before this change, the browser's back and forward
buttons would update the URL with the ID of the
desired slide, but the UI would not actually
update.

The problem was that the `open` method was getting
called for `onhashchange` events, but it would do
nothing if the carousel was already activated.
This patch adds a new method that will switch the
slide even if the carousel is already open.
Tiled Gallery: Don't wait for all images to load.

No need to wait for all images to load since we know their dimensions to begin with.
Tiled Gallery: JS object represents one gallery.

Refactored the Tiled Gallery prototype to represent a single tiled gallery as the name implies, and added a separate prototype to represent a collection of tiled galleries. This way it's clear which operations are done for individual galleries and which are done for all.
Tiled Gallery: Less responsibility for resize.

Extracted original-width and original-height attribute setting out of the resize function, and moved the call from resize to the constructor, since there is no need to see if the attributes are set in every resize call.
Tiled Gallery: Refactoring maybeSetSizeAttributes.

Made small changes to refactor the logic in maybeSetAttributes, since it was unnecessarily verbose.
REST API

Sticky posts should not be returned at the top of every /posts/ request. Only when requested.

Merges r96510-wpcom.
REST API: add `login` as part of the returned data of the author object in the API

Also adds a test for the new field
see https://[private link]

Merges r96537-wpcom.
REST API: add a new `/users` endpoint that allows the listing of users on a site, as well as just the authors of a site.

Also adds tests to make sure the endpoint works correctly in a variety of scenarios
See https://[private link]

Merges r96541-wpcom.
REST API: in the author return object, make the default for the `login` be an empty string instead of a zero, for consistency's stake

Merges r96543-wpcom.
REST API: move the `is_post_type_allowed()` function to be available for all endpoints as it will need to be reused in several `post` endpoints

All tests continue to pass with this change
See https://[private link]

Merges r96544-wpcom.
REST API / Tests

* stop vip endpoints from failing in production (in_testing only allows them to work on sandboxes. plus there are already access checks and marks for making the endpoints undocumented)
* FP bug: vip post was bumped to FP but couldn't display because it was using a CPT
* fix email one of the tests checks for since the author email is different

Merges r96545-wpcom.
REST API: introduce the ability to modify the post's author when creating or editing a post. The new param accepts the author ID or

Also introduces tests for the new paramater
see https://[private link]

Merges r96553-wpcom.
Jetpack: Nerf bad .svn folder remnants.
Merge pull request #497 from Automattic/remove-svn

Jetpack: Nerf bad .svn folder remnants.
Tiled Gallery: Fix square layout remainder margin.

Remainder would be short in width from the regular rows by exactly the margin. This is now fixed by not substracting the margin from the remainder size.
Tiled Gallery: Bottom margin fix.

The root cause of why the bottom/top margin between rows in Tiled Galleries is twice as wide as between columns turned out to be specific to the mosaic layout, where the rows actually had a concrete 2px bottom margin. If we remove this margin, we have a clean equal margin everywhere.
Merge pull request #495 from Automattic/jkudish-rest-changes

Changes from @jkudish and @justinshreve on the REST API.
Add jetpack_log_entry action.

This will let other plugins like Stream easily log what we’re logging
as well.
Bunch of minor JP admin css tweaks

- Fixed left aligned image bug in modals at mobile resolution.
- Decreased excess padding/margin around clouds at mobile resolution.
- Show activate/deactivate links in mobile view, works on hover in
desktop
- Fixed margin-top on filter button in mobile view
- Fixed white horizontal line when left nav menu is collapsed
- Changed message on homepage to no longer mention, “Once you’ve
connected Jetpack…” if you’re already connected.
Merge pull request #502 from Automattic/ui-tweaks-dave

Bunch of minor JP admin css tweaks