Improve Search commands

[Saladoc]

The /wiki and /docs commands both perform searches.

We should investigate if and how the search can be improved for users.

Possible techniques to explore:

• Auto-Completion for known Keywords / Classes
• Fuzzy Searches
• ...

[felldo]

To get the best experience from auto completion we should most likely start to cache the Javadoc and wiki and once in a while i.e. 1 hour interval refetch them automatically.

[Saladoc]

We can do it more often if the webserver hosting both understands If-Modified-Since headers. A small request every couple of minutes won't hurt if it gets answered with an empty HTTP 304 response most of the time.