The wiki-cache should have a file size limit

[xeekworx]

Currently, there is no limit to how big the wikicache file can get. This could be a problem. Two ideas:

• If I am going to cap the file size then dates need to be added to each of the query items so that the oldest items could be purged.
• The data could be separated in different files, each file having a soft limit.
• The content per query should also be limited. If the content exceeds a certain amount, then it should probably not get cached, this limit could be very high high; just to prevent someone from some how adding a query to the cache that's gigabytes. I'm not sure how that could be possible, but who knows.