Split SmppSession into SmppClientSession and SmppServerSession

[pgoergler]

SmppClientSession is created by a SmppClient to connect to a SMSC SmppServerSession is created by a SmppServer for an incoming connection from a ESME

So i put public SubmitSmResp submit(SubmitSm request, long timeoutMillis) into SmppClientSession interface.

[sebastienvermeille]

Good idea! It's a little bit confuse for beginners