Added Gif Database (Tumblr)

This is kind of cool, because now I can start adding any big Tumblr
repository of gifs, which should really open up the options. I'm also
thinking about making an 'omnibox' search instead of choosing different
engines, so there will be a single box to input a search tag. That
should load 'tonnes' of gifs, so in this case I'll need to implement a
'load more' function.

Also cleaned up some CSS, although one of the next steps is the
redesign... should be fun ;)