Bug when setting datum and coordinate conversion parameters

[davidhassell]

When setting datum and coordinate conversion parameters via the coordinate reference construct attributes, the new settings do not appear in the parent coordinate reference construct:

In [1]: import cfdm                                                                                          

In [2]: cr = cfdm.CoordinateReference()                                                                      

In [3]: cr.datum.set_parameter('test', 123)                                                                  

In [4]: cr.dump()                                                                                            
Coordinate Reference: 

[davidhassell]

This is fixed for version 1.7.9:

In [1]: import cfdm                                                                                          

In [2]: cfdm.__version__                                                                                     
Out[2]: '1.7.9'

In [3]: cr = cfdm.CoordinateReference()                                                                      

In [4]: cr.datum.set_parameter('test', 123)                                                                  

In [5]: cr.dump()                                                                                            
Coordinate Reference: 
    Datum:test = 123