Add residue_to_value protocol

[SebieF]

Implement residue to value protocol:

residue_to_value --> Predict a value V for each residue encoded in D dimensions in a sequence of length L. Input BxLxD --> output BxLxV

Also note #21 for the loss function and masking.

Most important point is to define a input data standardization. So definition of done:

• residue_to_value protocol implemented and tested
• data standardization is documented