Merge branch 'dev/DataObjID' into 'master'

update DataObjID

fixed typo in DataObjIDProperty, updated release notes, added DataHandle placeholder prototype class

* DataObjID: various classes used for DataObject and DataHandle identification
  * DataObjID: holds a unique key for an object in the store, with an internal
              representation as a hash for fast lookup.
              syntax is either Gaudi EDS path style "/path/to/object", or ATLAS
              style with (ClassID,"key") or ("ClassName","key")
              Collections of DataObjIDs are unordered_set<DataObjID,DataObjID_Hasher>
              typedef to DataObjIDColl
  * DataObjIDProperty: jobOpt Property handler for DataObjID and DataObjIDColl
  * DataHandle: prototype placeholder for DataHande class

See merge request !41