Merge the color schemes component from MP6. Introduces Light, Blue, and Midnight.

Color scheme selection on your own profile page gives you a preview and autosaves the selection.

Also introduces the usage of a preprocessor for core files, namely Sass. For 3.8, we will not expand its implementation past the color schemes. This does require Ruby as well as Sass 3.3.0+ due to the usage of the sourcemap option.

Note that only the default color scheme is available when running out of src. Use build to test the rest as well as the color picker.

props ryelle, melchoyce, tillkruess, drw158, littlethingsstudio, helen. see #25858, #22862.

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Inline documentation for hooks in wp-admin/includes/class-wp-comments-list-table.php.

props siobhyb, kpdesign.
fixes #25662.
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Turns out it helps if you add those pesky Sass files if you're going to use a preprocessor. see #25858.

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Bring in the widgets component of MP6. See #25858.

* A cleaner UI, with a simpler design for available and inactive widgets, and more emphasis on your sidebars.
* Available widgets and sidebars expand to two columns at larger screen sizes making it easier to manage sites with lots of sidebars.
* New dropzone indicator for empty sidebars.

Props shaunandrews, joen, iammattthomas.


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Update the Themes screen, merging THX into core.

 * Name: THX38
 * Description: Update the Themes screen with a new design and experience.
 * Tags: visually-focused, bigger-screenshots, fast, mobile-friendly, backbone-driven
 * Author: matveb, shaunandrews, melchoyce, designsimply, shelob9
 * URI: http://wordpress.org/plugins/thx38/

fixes #25948


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THX needs this file, for now. see #25948.

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Temporarily remove CSS preprocessing until we can get our Ruby dependency sorted out.

see #25858, #22862.

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Merge the new dashboard design into core.

Merges https://github.com/growthdesigner/wp-dash.

props lessbloat, joen, helen, dbernar1, kraftbj, ryelle, tillkruess, grapplerulrich, markjaquith.
see #25824.

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Move to grunt-sass, which which has less bells and whistles than grunt-contrib-sass but also no Ruby dependency.

see #25858, #22862, [26143].

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Avoid a notice when SCRIPT_DEBUG is not defined. props MikeHansenMe. see #25824, #25858.

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Remove SCRIPT_DEBUG reference from register_admin_color_schemes().

Instead, script-loader.php handles converting .min.css to .css when SCRIPT_DEBUG is on, and has since r21592. (This was done for compatibility with plugin color schemes that used .css and .dev.css.)

see #25858.

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Background Updates: Fix a PHP Fatal error which could be encountered on some systems when using FTP. Fixes #25817 for trunk.

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Background Updates: Spread them over the hour. Props Pento. Fixes #25833 for trunk 

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Twenty Fourteen: make sure styles for featured content on a static page are limited to posts within the main content area. Props iamtakashi, fixes #25938.
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Twenty Fourteen: remove unused class name, props obenland. See #25946.
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Twenty Fourteen: simplify and prefix post thumbnail sizes, props obenland. See #25946.
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Twenty Fourteen: first pass at adding help text to to "Help" tab for `edit.php` and `themes.php` screens. Props obenland for starter patch, see #25837.
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Twenty Fourteen: fix tabs to spaces in two files. See #25946.
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Background Updates: Add a 'automatic_updates_complete' hook that fires after any updates have run. Props pento. Fixes #25841

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Avoid jshint errors in edit-comment.js.

props adamsilverstein.
fixes #25979.

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