Versioning at the variable level

I would like to propose some versioning at the variable level of the DRS.

The current version is at the whole-of-dataset level, and thus does not appear to allow changes made to files for individual variables. One scenario is that, an error was discovered the algorithm that computed the RH diagnostics, and we would like to replace the files only for RH.

I recall that this idea was to be discussed with the CORDEX group to align with CORDEX DRS. However, since the ACS Level 1 will still be post-processed (e.g., for BARPA, regridding from 0.154deg to 0.2deg AUS-20) before submitting to CORDEX, we can have some flexibility here with the ACS Level 1 hosted in ia39.