[86] Spin off cipher_entropy project to decouple entropy generation from abstract cryptographic algorithms. This way, users may decide wether to use cipher_entropy or another entropy provider. It also simplifies cipher a lot because it has no longer need to differentiate between client and server implementations (all that stuff will be moved to cipher_entropy where there's more justification for complex user tweaking when using the library). (+1 squashed commit)

Note that this change will break compatibility although I don't expect much trouble in adapting to the new structure. Anyway, cipher is still in 0.x.x versions so everybody should have clear that breaking changes may arise from upgrade to upgrade.
[86] Change registration strategy to avoid differentiations between server
and client. Everything in cipher will be client/server independent as of
this commit (I hope ;-).
[86] Make drone.io work with new changes.