Topaz rean

[tdcwilliams]

• change topaz4 rean dataset so we can use reprocessed files downloaded from CMEMS. This gives the topaz4c version of the reanalysis. (Main change is to the modern variable names and we now use a single file for both nodes and elements.)
• change path to link into $NEXTSIM_DATA_DIR/oceanic_forcing instead of $NEXTSIM_DATA_DIR itself (easier to see contents of $NEXTSIM_DATA_DIR directory)
• for ERA5 link into $NEXTSIM_DATA_DIR/atmospheric_forcing instead of $NEXTSIM_DATA_DIR itself

[tdcwilliams]

An extra comment on this pull request:

For most forcings, the old way of linking into NEXTSIM_DATA_DIR will still work so you won't need to change anything.
Also for most forcings, there will be no longer a need to link and paths can be put in the config file. eg for topaz4 and ERA5
reanalysis on fram.sigma2.no

[setup]
atmospheric_forcing_input_path=/cluster/projects/nn9878k/sim/data/ERA5_DROWNED
oceanic_forcing_input_path=/cluster/projects/nn9878k/sim/data/TOPAZ4_reanalysis-merged_30m

The exceptions are the forecast forcings when using the current python code for running the forecast, which still has some hard-coding in it (should be updated before too long). Anyway, it will currently work with these options for the nextsim config file

[setup]
atmospheric_forcing_input_path=ECMWF_NRT
oceanic_forcing_input_path=TOPAZ[4,5]RC_DAILY