Fixes bug in get_naming_and_values and get_naming_and_values_2D where we got a KeyError    if 'Experimental Metadata' group did not exist in Experimental Data group.
Fixes bug in get_naming_and_values and get_naming_and_values_2D where we got a KeyError
   if 'Experimental Metadata' group did not exist in Experimental Data group.

QudevETH/PycQED_py3