* Fix public key part in echo server example
* Remove unused Plaintext session class
* Rename Plaintext header guards
* Fix illegal comparison in crypto provider impl
* Implement SECIO
* Switch Kademlia to boost::optional instead of std
* Add -insecure option to echo server
* Add MessageReadWriterBigEndian
* Add SECIO cases to host_integration_test
* Add SECIO marshallers tests
Possible Drawbacks
Not possible to perform cross-implementation testing by now (go implementation of libp2p got updated much so c++ implementation needs to be changed too).
P521 curve-based algorithm could be faulty - needs to be tested when cross-implementation testing gets possible.
User's callback could be called twice in case of error inside secureInbound and secureOutbound methods - this could be easily fixed if we count this as an issue.
Signed-off-by: Igor Egorov <igor@soramitsu.co.jp>
Igor Egorov
Bohdan