Add Maximum Size Setting for File Store

Usecase:

Whe caching large amounts of data, you can use passivation to the file store to extend the size of the cache without additional memory requirements. However, since it's not possible at the moment to limit the size the file store grows to, this might lead to an overflowing disk.

Enhancement:

It would be great to have settings for the file store that limit the total number/size of entries in the cache including the entries that have been passivated to the store. (similar to the settings for the in-memory cache)