Fix LRUCache: It wasn't even behaving as LRU because I forgot to push the key to top in get().
Notice: This class isn't even being used by fred according to Eclipse "References > Project". So you don't need to check for side effects when merging this.
IIRC I implemented this for Freetalk. I started working on it again for the WOT cache which I plan to implement
LRUCache: Make expiration time optional. Needed for WOT branch "caching".
LRUCache: Add .clear(). Needed for WOT branch caching.