MuonReadoutGeometry - Identifier clean up & AthMessaging

• Inherit the MuonReadoutElement from AthMessaging to avoid on-the-fly creation of the MsgStream objects
• Pull setIdentifier to the MuonReadOutElement
• Add getStationIndex() method to replace the bulk usage of the getStationName() in the near future
• Number of MDT/CSC/RPC/TGC elements in a station is obsolete --> removed
• Remove duplicated collectionHash(), identifyATLAS() methods
• IsMirrored() and isDetDescNegZ() are only used in the RpcReadoutElement pull them into this class
• Remove ancient AMDB identifiers: getAmdbZi() and getAmdbFi()