NEW: updated SiteStatus to use RSSCache
NEW: RSSCacheNoThread renamed to RSSCache ( and deleted former one ),
new SiteStatus helper. Internal representation of CE as ComputingElement
NEW: upgraded Status helpers to have the same signature
NEW: ported method from ResourceStatus, so that can be reused
NEW: base class for the Status helpers of RSS
Merge pull request #1426 from ubeda/v7r0_SiteStatus

[V7r0] NEW: Site status