INT-2863 Add Release Strategy to Resequencer

- allow the configuration of release strategies on resequencers
-- adjust the xsd to allow the definition of a release strategy
-- move release strategy parsing to AbstractCorrelatingMessageHandlerParser
-- add unit tests

For reference see: https://jira.springsource.org/browse/INT-2863

INT-2863 Polishing

Fix white space; add @author; update copyright.

INT-2863 Resequencer/Aggregator Docs

Add docs for correlation and release strategis to Resequencer.

Add *.expression docs to Aggregator.
Merge pull request #696 from ferstl/INT-2863