Make EventBase abstract

Fix: The EventBase class is abstract.
Move AcceptionPredicateEvent into AcceptionPredicateExtension

Fix: Made the AcceptionPredicateEvent class an inner class of AcceptionPredicateExtension.
Fix some small issues in AcceptionPredicateExtension

Fix: The AcceptionPredicateExtension.APELocalHandlerSendInterceptor class is static for slightly increasing performance.
Fix: Resolve some variable shadowing issues.
Add javadoc to AcceptionPredicateExtension

Add: The required javadoc for the public api of AcceptionPredicateExtension.
Rename AcceptionPredicateExtension to SendPredicateCheckExtension

Add: Rename the AcceptionPredicateExtension class to the more expressive "SendPredicateCheckExtension".