Use a brighter blue against dark backgrounds in the admin menu and toolbar.

Not only does this pass contrast guidelines, but it also visually appears closer to the original highlight blue used against light backgrounds.

props melchoyce. fixes #30323.

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git-svn-id: http://core.svn.wordpress.org/trunk@30312 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Fifteen: adding context to page links for screenreaders.

Props afercia, fixes #30174.


Built from https://develop.svn.wordpress.org/trunk@30314


git-svn-id: http://core.svn.wordpress.org/trunk@30313 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Fifteen: since color schemes can be customized let's call them base color schemes instead of just color schemes.

Props celloexpressions, iandstewart, fixes #30316


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git-svn-id: http://core.svn.wordpress.org/trunk@30314 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Fifteen: adding context to pagination links for screenreaders.

Props afercia, iamtakashi, fixes #30152


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git-svn-id: http://core.svn.wordpress.org/trunk@30315 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Fifteen: improve appearance of page links when there are tons of pages to link to

Props iamtakashi, fixes #30301


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git-svn-id: http://core.svn.wordpress.org/trunk@30316 1a063a9b-81f0-0310-95a4-ce76da25c4cd
TinyMCE: enhance the inline toolbar for images:
- Add alignment (left, center, right, none) buttons.
- Position the menu above the image when possible, except on iOS.
- Fix selecting images on iOS.
First run, part props avryl. See #30147.
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git-svn-id: http://core.svn.wordpress.org/trunk@30317 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Fix typo in translatable string, see #30147.

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git-svn-id: http://core.svn.wordpress.org/trunk@30318 1a063a9b-81f0-0310-95a4-ce76da25c4cd