Added Plupload for the "Image" content block. Still needs the ajax callback to get the file, add it to wordpress, and return to the post. Proper UI response when drop a file is needed too.

git-svn-id: https://plugins.svn.wordpress.org/wp-content-blocks/trunk@855207 b8457f37-d9ea-0310-8a92-e5e31aec5664