Relicensing original code to CC0

[mratsim]

@jrhea @prestonvanloon, I assumed that you were OK with relicensing your MIT/Apache contributions to the starting scripts to nim-beacon-chain to CC0.

I choose CC0 just to be the same as the eth2.0-specs repo but I'm not really a lawyer.

[prestonvanloon]

I declare that I am OK with re-licensing my contributions in this repository (run_prysm.sh) to a more permissive license.

[djrtwo]

CC: @jrhea