Esmval fixes

[ellesmith88]

No description provided.

[ellesmith88]

It would probably make sense to update fixes where the operands are a list of dicts, to just be a dictionary (and update as needed in roocs/daops#40).

e.g. change

{"attrs": [ {"long_name": "Dissolved Oxygen Concentration"},        
          {"standard_name": "mole_concentration_of_dissolved_molecular_oxygen_in_sea_water"} ]    
}

to

{"attrs": {"long_name": "Dissolved Oxygen Concentration",        
           "standard_name": "mole_concentration_of_dissolved_molecular_oxygen_in_sea_water"}        
}

This is what I have used with subsequent fixes e.g. for decadal data. This also requires the fixes to be updated in the elasticsearch fix store.

EDIT: I have made this change