Twenty Fifteen: adding context to page links for screenreaders.

Props afercia, fixes #30174.


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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