Multiple improvements to image post format insertion and display.

* get_tag_regex() altered based on Unit Tests.
* Changes to post-formats.js to provide size and link context during image selection.
* Captions are now output in the_post_format_image() when present.
* The meta value for url is respected for the image post format when the HTML in the image meta doesn't include a link

props wonderboymusic. fixes #23965, #23964. see #24147, #24046.

git-svn-id: https://core.svn.wordpress.org/trunk@24066 1a063a9b-81f0-0310-95a4-ce76da25c4cd