New feature: search the old forum

The old, official forum may be closed and dead for good, but it is still a huge kind of encyclopedia/collection of memories for some which can be useful when you want to look something up/are feeling nostalgic. So, the other day while I was bored, I decided to add an embedded search bar and it's now in the Navigation Bar at the top of the page.

Many thanks to orealo for helping out with the javascript stuff!

And now let's hope Team Editors don't take the forum offline.