re-instate specific acroecosystems

[teixeirak]

In the previous version, we had several specific crop agroecosystems: maize, soy, sugarcane, switchgrass, miscanthus, but they have now disappeared.

We have range maps, model parameters, and biophysical data for these, so it would be worth re-instating these.

However, we're not going to hold up publication for these.

Issues #101 and #27 both relate to this. I will now close those issues, as they are currently defunct.