add parameters.json to base cabs, add env section to parameters.json

[o-smirnov]

Stuff like this: https://github.com/ratt-ru/Stimela/blob/respect-the-environment/stimela/recipe.py#L276

...is better expressed as an abstract "what environment variables does this cab need?" specification. I suggest adding an optional "env" dict to parameters.json. If present, the recipe code will set these variables in the environment of the cab (using the existing add_environ() functionality).

Furthermore, since this sort of thing (as is the "junk" setting, as are the output wranglers) tends to be the same for e.g. all CASA-based cabs, it would be cleaner, and less effort, to set it up at cargo/base level rather than cargo/cab level.

What you need then is a "parent" parameters.json dict at the base level. The child would inherit the parent's parameters.json dict, and override/augment it with its own. The recipe code then needs to read the dict from the parent first, then do an update() on it with the dict of the child.