Improve localization for `WP_Date_Query` error strings.

* Don't create an extra variable for the string when it's only used once.
* Avoid using `<code>` HTML tags inside of translatable string.
* Improve data types and escaping on sprintfed values.

Props dd32.
Fixes #25834.

git-svn-id: https://develop.svn.wordpress.org/trunk@30300 602fd350-edb4-49c9-b593-d223f7449a82
Correct grammar error in `WP_Date_Query` error message.

Props Offereins.
See #25834.

git-svn-id: https://develop.svn.wordpress.org/trunk@30301 602fd350-edb4-49c9-b593-d223f7449a82
Twenty Fifteen: simpler CSS by using divs instead of spans for menu descriptions.

Props philiparthurmoore, fixes #30296



git-svn-id: https://develop.svn.wordpress.org/trunk@30302 602fd350-edb4-49c9-b593-d223f7449a82
Twenty Fifteen: create consistent spacing with embeds and images.

Props afercia, fixes #30286



git-svn-id: https://develop.svn.wordpress.org/trunk@30303 602fd350-edb4-49c9-b593-d223f7449a82
Twenty Fifteen: simplify the code used to generate screen reader text for the is_home title.

Props davidakennedy, fixes #30305



git-svn-id: https://develop.svn.wordpress.org/trunk@30304 602fd350-edb4-49c9-b593-d223f7449a82
Twenty Fifteen: Minor formatting and docs tweaks, clearer variable name.

Props celloexpressions, see #29988



git-svn-id: https://develop.svn.wordpress.org/trunk@30305 602fd350-edb4-49c9-b593-d223f7449a82
Customizer: When navigating around the site within the Customizer preview, update the document title.

props westonruter.
fixes #28542.

git-svn-id: https://develop.svn.wordpress.org/trunk@30306 602fd350-edb4-49c9-b593-d223f7449a82
Customizer: Use `jQuery.fn.toggle()` instead of `slideUp`/`slideDown` if panel/section/control is not inserted into DOM yet.

jQuery does nothing when calling `slideUp` on elements that are not inserted into the DOM yet, which can now be the case now when first loading the Customizer as the panels, sections and controls get dynamically inserted, see #28709.

props westonruter.
fixes #30251.

git-svn-id: https://develop.svn.wordpress.org/trunk@30307 602fd350-edb4-49c9-b593-d223f7449a82
Customizer: Trigger `widget-added` event when initializing.

Widget controls are now added to the pane dynamically via JavaScript, see #28709.
Remove the event trigger from `SidebarControl.addWidget()` as it's covered by `WidgetControl.ready()`.

props westonruter.
fixes #30236.

git-svn-id: https://develop.svn.wordpress.org/trunk@30308 602fd350-edb4-49c9-b593-d223f7449a82
Customizer: Add support for the media library in Background Image controls.

`WP_Customize_Upload_Control` (PHP) and `api.UploadControl` (JS) can now open the media modal.

props celloexpressions, and ericlewis for docs.
see #21483.

git-svn-id: https://develop.svn.wordpress.org/trunk@30309 602fd350-edb4-49c9-b593-d223f7449a82
Always use a full filesystem path when including the FTP handler in PemFTP. This prevents other files in the includes directory being scanned/included accidentally.
See #29628


git-svn-id: https://develop.svn.wordpress.org/trunk@30310 602fd350-edb4-49c9-b593-d223f7449a82
PHP 5.2 compatibility for [30310], __DIR__ wasn't added until PHP 5.3. Props TobiasBg. Fixes #29628


git-svn-id: https://develop.svn.wordpress.org/trunk@30311 602fd350-edb4-49c9-b593-d223f7449a82