Added test of Globus Catalog transfer members
Added _getattrs to NeXusTree and renamed index variables
Added lock and unlock menu items

Changes a file's open mode to readonly and read/write respectively.
Fixes a problem with doing deep copies of tree items

This would make the tree item different from the shell, so I no longer
call the super.__setitem__, which triggers the copy. Also adds lock and
unlock contextual menu items.
Changed read/write behavior

If the HDF5 file is opened as read/write, changes are now automatically
made to the file.