Document the environment needed to get apd

At the moment nobody can go and use this package apart from the developers. Indeed nowhere it is said that one should use lb-conda. Then I had to check a few environments and realised that apd is available with lb-conda default but not for example with lb-conda DPA/analysis-productions, which I was not expecting. This should all be documented.

Corollary: clearly I had misunderstood what the env DPA/analysis-productions is for. Where can I find a basic explanation of what the envs are? lb-conda --list tells me the env available but gives me no hint as to what to choose. OK, this is beyond apd but I thought I would mention the issue since I bumped into it just now.