Drop ObsView etc.

[darsnack]

Should we drop DataView and ObsView? Most of the data iterators can be implemented without them, and I think we should minimize the number of extraneous (abstract) types.

[CarloLucibello]

Should we drop DataView and ObsView?

I'd like to, but I tried to obtain the same functionality with

for x in datasubset(data) ...
# or 
for x in DataSubset(data) ...

but it's not quite the same as iterating over ObsView since x is still a DataSubset

I think we should minimize the number of extraneous (abstract) types.

agree.

[darsnack]

That's because of the following override for DataSubsets:

# override AbstractDataContainer defaults
Base.getindex(subset::DataSubset, idx) =
    DataSubset(subset.data, _view(subset.indices, idx))

We could get rid of this. I am not sure what is to be gained by this override.