TODO list for MeshLink
----------------------
-* Write meshlink_sign() and meshlink_verify(). These should just call
- ecdsa_sign() and _verify(), with mesh->self->connection->ecdsa as the key for
- _sign(), and node->ecdsa for _verify()?
-
* meshlink_join():
- add checks that we only join another mesh if we did not connect to any other node before.
- only allow meshlink_join() when the library thread is not running.