Implements Base core CEP Engine

CEP Engine is a base building Block in Complex Event Processing systems.
Logger Optimization

Use slf4j instead commons.logging. It provide additional capabilities over log4j.
Statement Code Optimization.

Clean redundant code implementing a better Statement classes hierarchy.
Merge branch 'feature/Statement' into develop

Implements Rotary Core base classes
[ListenerBase] Module skeleton created
[ListenerBase] Created listener base classes

This abstract classes hide the Esper event recovering and mapping allowing to concentrate in the listener business logic.
[ListenerBase] LogListener implemented

Basic Listener used to log event information.
It allow better EPL testing logging event info when EPL is triggered.
Merge branch 'feature/ListenerBase' into develop

Add Base Listener functionality.