Added replace attribute functionality.
Merge remote-tracking branch 'origin/gda-8.40'

Conflicts:
	org.dawb.hdf5/src/org/dawb/hdf5/HierarchicalDataFile.java
	org.dawb.hdf5/src/org/dawb/hdf5/IHierarchicalDataFile.java
	org.dawb.hdf5/src/org/dawb/hdf5/nexus/NexusUtils.java