Add script to create namelist_definition_mpas_dycore.xml from MPAS-A Registry.xml

[gdicker1]

What is the feature/what would you like to discuss?

The namelist_definition_mpas_dycore.xml file being discussed in #248 was generated by a Python script using a MPAS-A Registry.xml as input. To ensure consistency and enable other developers to easily update the namelist definition for MPAS-A as a dycore, this script should be added to CAM-SIMA.

Original version of the script: https://github.com/gdicker1/TranslateXML_MPAStoCAMSIMA

Is there anyone in particular you want to be part of this conversation?

@nusbaume @mgduda @kuanchihwang

Will this change (regression test) answers?

No

Will you be implementing this enhancement yourself?

Yes