Create training datasets list

[benscott]

List of training datasets, both existing online resources and those produced for SDR.

[llivermore]

Any datasets should go into the separate datasets repository: https://github.com/DiSSCo/sdr-datasets

We are not using any additional datasets, but if we do they should go into the documentation/wiki for the datasets repository

All the datasets created with Teklia are ready to be incorporated into the datasets repository and are in Teklia GitLab.