SERVER-11636: move NamespaceDetails::storageSize to Collection
SERVER-11636: remove Extent::getNextExtent and Extent::getPrevExtent
remove DataFileMgr dead code
SERVER-11643: remove nsdetails from s/ by moving averageObjectSize to Collection
SERVER-11643: remove nsdetails from mongodump
SERVER-11643: reorganize touch to be a bit cleaner and use newer idioms
SERVER-9469: more efficiently set ns in CurOp
SERVER-11643: clean up includes
SERVER-11643: make Collection::storageSize return int64_t to be consistent