Analytics plugin v1

remove old analytics code from ubersystem, this is all being redone / moved into https://github.com/magfest/uber_analytics

add in an extra place for more stuff to be put into ```<head>``` tag in base.html
I wouldn't want to reference analytics specifically since the idea behind blocks is that they should be generic.  But I do agree that ``head_additional`` is pretty vague and a more semantic name would be better.

Really what we should do is add a bunch of empty blocks into our base everywhere that we could conceivably imagine a plugin needing to inject content.  That way we won't have to update the main repo every time a plugin wants to jam something somewhere on the page.