Use EventWrapper.stop() instead of the native event
Clean up some unused stuff in pom.

build against tapestry5-alpha-26 and newest pluto version

Move tapestry dependencies to scope "provided" projects using the portlet bridge should declare their tapestry 5.4 dependency versions explicitly.
Fix unit tests, most fixes were timing related. Ajax Form Loop test still fails due to https://issues.apache.org/jira/browse/TAP5-2228

It has been tested with a patched tapestry version locally and everything completes then.