Configuration/Serialization refactoring

Currently Infinispan's configuration parsers and serializers rely on XmlStreamReader and XmlStreamWriter from java.xml directly. This means that supporting other formats (JSON, YAML) requires writing parallel implementations.
Additionally, referencing java.xml pulls in 200 classes which have an RSS impact of about 20MB.
We should refactor the parsing/serialization code so that it can support multiple formats.
The XPP3 implementation is very compact and doesn't rely on the internal java.xml classes.
Identify other modules which may pull in XML classes and try to avoid that.