Server-side netty channels and now synchronous
Refined control flow mechanism to also oversee the number of pending replie waiting to arrive at clients.

Refined AsyncServiceProxy to process ACKs in a separate thread, allowing it to be totally asynchronous from the perspective of the developer.
Also refined AsyncLatencyClient to wait for all replies to arrive before closing proxies.

Removed FIFOExecutable, since it was a redundant interface that was pratically the same as the Executable interface
Added more comments to some classes
Updated javadoc

Cleaned up the algorithms for hmac, secret keys, signature and hashing.
Added parameters at config/system.config for the above algorithms.

It is now possible to supply to the library a custom key loader to replace the original RSA key loader.
This is useful for applications that also need to use and manage the same structure of keys as the library and/or to use different public key algorithms/providers.
This was done by creating a new interface "KeyLoader" and extending the ServiceProxy and ServiceReplica constructors with parameters to pass objects that implement the interface.
If a null object is passed, the library will simply load the default RSA key loader.

Also replaced all System.out.println and ex.printStackTrace methods with adequate SLF4J invocations.
Included xml configuration file for logback.

Fixed a bug in the AsynchServiceProxy class that would case a race condition between the client and the servers: the client would store its sequence number after sending its requests, but if the servers responded quickly enough for the client to parse the replies before storing the sequence number, the messages would be discarded.

Also edited a logging message and added another one.

Do not panic! I only added descriptions in the comments' header for each of these classes. Also removed a few unnecessary 'import's.