added staic computeJFKSharedKey. Started to add JFK to KeyExch
Removed Duplicated stripBigIntegerToNetworkFormat() code. the method is now a public static in DHLightContext. Also include commented out
code for benchmarking the fastest HMAC provider against the HMAC class. As the class can not process multiple byte[]s easily, there is no
easy way to effectivly benchmark them against eachother.