Ensembles now need feeding from ENVS

[JimCircadian]

The model-ensembler configurations need dynamic configuration by run_*_ensemble commands from ENVS to avoid manual reconfiguration for BAS and JASMIN.

It's always the case that this will be difficult to map through and automate, so these are the only use cases. This should be clear from the README.

• Update run_train to map ENV configuration into the ME template
  • Partitions
  • Job length
  • Nodes
• Update run_predict to map ENV configuration into the ME template
  • Partitions
  • Job length
• Update README to make specific that these use cases will likely need adapting for other HPC systems (if SLURM)