Svg-painter:
- Clean up the JS, better names, etc.
- Convert the base64 encode/decode code from jQuery plugin to local use.
- Add missing icon colors for the default theme.
- Make it more error-proof.
Fixes #26333.
Built from https://develop.svn.wordpress.org/trunk@26601


git-svn-id: http://core.svn.wordpress.org/trunk@26491 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Utilize a more widely-adopted CSS method for hiding screen reader text, as seen in projects like jQuery UI and HTML5 Boilerplate. props codebykat for the initial patch. fixes #23684, #26107.

Built from https://develop.svn.wordpress.org/trunk@26602


git-svn-id: http://core.svn.wordpress.org/trunk@26492 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Svg-painter: fix couple of jshint warnings, see #26333.
Built from https://develop.svn.wordpress.org/trunk@26603


git-svn-id: http://core.svn.wordpress.org/trunk@26493 1a063a9b-81f0-0310-95a4-ce76da25c4cd