Two parts PR because I got impatient - sorry it doesn't make the PR very clear

Renaming

After discussing with Qi, and ahead of a final documentation effort, renaming of some elements appeared necessary:

FeatureInput --> UdaoInput and same for anything prefixed with Feature. The reason for that is that what we called FeatureInput is the real minimum necessary for the whole UDAO pipeline, i.e. having feature input that can be used to infer variables
UdaoInputShape is renamed UdaoItemShapebecause it also contains output shape
UdaoInput.feature_input renamed to features for brevity. Consequently, feature_input_names is renamed feature_names
What was called UdaoInputis called UdaoEmbedInput

GPU operations

add device as a parameter for problem.apply_function, derive_processed_input, derive_unprocessed_input
output floats instead of tensors (unnecessary) in BaseProgressiveFrontier._form_obj_bounds_dict
compute the objecives on CPU in BaseProgressiveFrontier._compute_objectives
add to(device) method to OptimizationElement and UdaoInput to be able to move them around devices easily.
in MOGD, move tensors and modules to MOGD.device
change tests to bring values to cpu for assertion.