Splitting the protocol into phases

[mimoo]

The prover protocol is starting to get a bit long. It might be a good idea to split it into different phases (associated to different functions in the implentation). What about:

1. circuit processing (padding and zk of circuit)
2. compute and commit
3. evaluate

Or we could even further divide:

1. circuit processing
2. compute and commit parts of the circuit
3. evaluate
4. compute the linearization
5. evaluate the linearization
6. create the aggregated evaluation proof