Make Twenty Fourteen the default theme. props markmcwilliams. fixes #25702.

git-svn-id: http://develop.svn.wordpress.org/trunk@26024 602fd350-edb4-49c9-b593-d223f7449a82
Add es3 and onevar to the JSHint configuration as discussed in IRC. Props jorbin, see #25187.

git-svn-id: http://develop.svn.wordpress.org/trunk@26025 602fd350-edb4-49c9-b593-d223f7449a82
Twenty Fourteen: add full-width featured images for layouts without a content sidebar, but use `wp_is_mobile()` to load smaller-sized images for mobile. Props iamtakashi, fixes #25758.

git-svn-id: http://develop.svn.wordpress.org/trunk@26026 602fd350-edb4-49c9-b593-d223f7449a82
Fix inverted logic for displaying the 'Broken Theme' string. props pavelevap. fixes #25465.

git-svn-id: http://develop.svn.wordpress.org/trunk@26027 602fd350-edb4-49c9-b593-d223f7449a82
A negative term parent value should be sanitized to 0, not 1. Fix a regression in sanitize_term_field() caused by [26010].

props mattheu for initial patch.
fixes #25852.

git-svn-id: http://develop.svn.wordpress.org/trunk@26028 602fd350-edb4-49c9-b593-d223f7449a82
Add X-UA-Compatible meta tag in the admin, locking the compatibility mode in IE to the highest supported document mode. Fixes #25575.

git-svn-id: http://develop.svn.wordpress.org/trunk@26029 602fd350-edb4-49c9-b593-d223f7449a82
Twenty Fourteen: minor template fixes and a placeholder screenshot.

git-svn-id: http://develop.svn.wordpress.org/trunk@26030 602fd350-edb4-49c9-b593-d223f7449a82