delete useless size in CachingFreenetStore and use isEmpty
use isEmpty instead of getSize in CachingFreenetStoreTracker and push a limited number of keys instead of one push in add
CachingFreenetStoreTracker: add "|| maxSize == 0" in the assert in add() function because if maxSize == 0 we have a queuedJob = false
use a "final int sizeBlock;" set at construction, instead of getSizeBlock() in CachingFreenetStore