Ensure "cascade" mapping is set for ResolveTargetDocumentListener

ResolveTargetDocumentListener expects $mapping['cascade'] to be set, while it previously may not have been depending on how the ClassMetadata was defined (the "isCascade*" fiels were always set).

This also makes the cascade handling consistent with ORM.
Merge pull request #888
Add ResolveTargetDocumentListener section to 1.0.0-BETA10 changelog
Update changelog for 1.0.0-BETA11