DONT MERGE YET... Review for now

  - Adapted `Store` SPI to current `Cache` API
  - `Ehcache` delegates to `Store` and handles `CacheAccessExceptions`
Are you saying that since it's `Store.ValueHolder` it shouldn't be it's responsibility ? Also, what I meant or understood, when having that role on `Cache`, was that it was its responsibility to honor it, i.e. return `null` as well as fire any kind of `Listener`... I wasn't explicitly referring to the `.isExpired()` logic really...