Cosigner token collision

[nodech]

It's required that cosignerToken be truly random, so other cosigners can't guess the token.
BUT if two cosigners choose same cosigner token, it will be a conflict and authentication does not handle that correctly.

Probably after wallet is finalized we should invalidate wallet if two tokens are same.
Or add additional information on authentication to let you choose the cosigner you want to authenticate with.

@BluSyn