Fix setProperty in CaloSinglePhotonAlg
CaloSinglePhotonAlg invokes a setProperty of a DataObjectHandle, to only change one of the four options (i.e. the default location, leaving mode, optional and alternate invariant). This patch does this correctly (previous code would nullify the mode, optional and alternate tokens, which then prevents the parser from properly parsing the property), albeit in an ugly way due to the syntax required...
Depends on Gaudi!16 (merged), and this is a superset of !90 (merged), so that should be merged first...