DROF and DATM stream names

[aekiss]

generate_xml_datm.py produces stream names like this

  <stream_info name="CORE_IAF_JRA55do.PRSN">

which is confusing, because CORE is a different dataset from JRA55do, and also the same stream names are also used for the RYF configs. Can we drop CORE_IAF_ and just have names like this?

  <stream_info name="JRA55do.PRSN">

Similarly, generate_xml_drof.py uses

  <stream_info name="rof.iaf_jra">

but

  <stream_info name="JRA55do.FRIVER">

(and similar for LICALVF - see #29) would be less confusing and more consistent.

[dougiesquire]

I think we can change these here, but CORE_IAF_JRA55do is actually the name of the new datamode that @ezhilsabareesh8 set up, so if we don't like that name we should change it here also.

UPDATE: opened COSIMA/access-om3#219

[dougiesquire]

Closed by #31