Twenty Fourteen: Add styles and support for the new block-based editor.

This update adds styles and theme support related to the new block-based editor to enhance the experience of using it with Twenty Fourteen.

These are the specific changes made to this theme:

- Add `blocks.css`, to style blocks on the front end, to make sure they match the theme’s existing HTML element styles.
- Add `editor-blocks.css` to style blocks in the editor, to make sure they match the theme’s existing HTML element styles.
- Add theme support for `editor-styles`, to pull the existing editor stylesheet into the new editor.
- Add theme support for `wp-block-styles`, to load the default block styles on the front end.
- Add theme support for `editor-color-palette`, to load a color palette based on the theme’s color scheme into the block-based editor. 

Props laurelfulford, crunnells, ianbelanger, davidkennedy.

Merges [43797] to trunk.

Fixes #45042.
Built from https://develop.svn.wordpress.org/trunk@44144


git-svn-id: http://core.svn.wordpress.org/trunk@43974 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.1-alpha-44143';
+$wp_version = '5.1-alpha-44144';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.