Change api into interactive+non_interactive

[maurges]

The diff is too big as the indent changed. Please look at shared_state especially, did I understand correctly what you wanted from it

[survived]

(I didn't verify that proofs implementation match their definition, I plan on reviewing it after cggmp is implemented)

[maurges]

I initially thought returning challenge would be useful for tests, to check that challenge derivation is the same in both places. But then I didn't even check that. Yeah, let's remove it

[maurges]

Now only have to figure out this thing with 2q

[survived]

Now only have to figure out this thing with 2q

Are there any difficulties with that? I though you can just multiply q at 2 and that's it