Feature extraction functionality

[MaximeBouton]

The current functionality does not support easy logging of features.
Instead we suggest to use DataFrames.

the package would export a feature extraction function:

extract_features(list_of_features, scenes, ids) 

that would return a namedtuple with IDs as keys and a dataframe as values. The column names are automatically determined from the list_of_features given by the user, as symbols.

A feature consist of a type and an extract_features function describing its behavior on a single scene.

[MaximeBouton]

We might want to add roadway as the list of arguments.

[MaximeBouton]

One drawback of using strings or symbol to represent the list of features is that it might be complicated to pass in feature types like "distance to :bob", which would be straightforward by having a type:

struct DistanceToFeature{I} <: AbstractFeature 
    id::I 
end   

# then you could pass DistanceToFeature(:bob) (the naming is a bit awkward)