Use set and dict instead of list

[BenjaminRodenberg]

Using a set or dict would avoid duplicate entries in the schema. A list generally allows duplicate entries.

Additionally navigation using a dict is more comfortable than for a list.

I started this discussion in #18 (comment) but we should continue here to avoid getting off-topic over there.

[MakisH]

@vidulejs tried converting the list of read/write fields to dictionaries in the OpenFOAM adapter, and this seems to be possible and actually necessary, if we want to add type and operation to each exchanged data field.

[uekerman]

@MakisH Could you elaborate more why it would be necessary? This seems like a critical point we need to understand better.

[MakisH]

@uekerman the issue is exactly what you already guessed in another comment: in OpenFOAM, we can read either a Dictionary or wordList. The wordList only accepts strings. Anything more complicated is a Dictionary.

Maybe we just need to distinguish here between the theoretical definition of a dictionary and the concrete implementation in each context.