Implement remove-function in cache.js

[aro]

Implement remove-function in cache.js. This should remove one single entry in the cache:

cache.remove('key');

Also implement a regexp alternative that implements multiple keys.

cache.removePattern('a.+');

The implementation of the last one should do the following:

1. Get all keys
2. Filter the keys with regexp
3. Use cache.invalidate(keys)