integrate the DAGA work into kyber

[sarkortrantor]

Implement something in a similar way as https://github.com/dedis/kyber/blob/master/share/dkg/rabin/dkg.go
into the student_18_daga/sign/daga directory.
Only main structures - no networking / json methods
port it to dedis/kyber#master: https://github.com/dedis/kyber/wiki/Migration-from-gopkg.in-dedis-crypto.v0
Define methods on these structure
Write (or copy) the corresponding tests

[sarkortrantor]

not sure why kyber/sign/daga is the right place, to me DAGA is not a cryptographic primitive but an authentication scheme

[sarkortrantor]

other concern: now that I see that there are things in kyber like kyber/proof/ that defines stuff and interfaces to support Sigma-protocols and discrete logarithm proofs in the Camenisch/Stadler framework.
it seems that the daga code should use those things

[sarkortrantor]

TODO:
-first: port the existing code to use current kyber things (and familiarize with daga and the daga implementation)
-second: try to split things and put them in kyber / cothority

[sarkortrantor]

#5

[sarkortrantor]

#6

[sarkortrantor]

#3