Monday commit

Committing work to date: not really functional, still in the realm of
experimentation.

Implements:
* replacing bookmarklet code available in /wp-admin/tools.php by our
own (props @georgestephanis for suggestion and code)
* have all functionality take over /wp-admin/press-this.php
* have Press This run into an in-page modal, with a popup fallback when
the current page is SSL-enabled, but the target WP instance where Press
This runs is not.
* basic proof of concept of function to sort through and prioritize
sent media
* etc