Adds BlockUI, a JQuery plugin

This commit adds the latest version (2.61.0-2013.06.06) of BlockUI, a popular JQuery plugin (http://www.malsup.com/jquery/block/). The library was downloaded from the website, but is also available from Github.

The [GIT repository](https://github.com/malsup/blockui) is currently starred 698 times and forked 155 times.

Minified the source with Uglifyjs, as the author doesn't offer a minified version. Original unminified version is also included.