Store lazy blocks data in the cache storage not in the session

[kanevbg]

Because it is simply wrong to mix two storage types with different purposes.

Lesti FPC is caching software. Session storage is for simpler and crucial data of the application and not the caches. If the cache is flushed the session storage will be holding unnecessary data. Using session for caches will push much more IO on this storage. Sessions are diamonds in the web and should be keep as simple and available as possible. Working on clearing the sessions on background will not be good decision. It is better to delete the related caches from cache storage trough the cache API if a session gets invalidated. If there is any difficulties with this kind of implementation I will be glad to discuss and help.