Chained transformers

This adds support for chained transformers to wildfly-core.
The core model transformers have been rewritten to use chained transformers, and also the subsystems that are part of core: remoting, jmx and logging (although the logging transformers were written so nicely the benefit there is quite small). This has been tested in wildfly-core using 

      mvn clean install -Djboss.test.transformers.subsystem.old -Djboss.test.transformers.core.old -Djboss.test.transformers.eap

which enables the transformers tests for all legacy versions in the subsystem tests and the core model tests. I've also run the wildfly mixed-domain tests against a snapshot of wildfly-core and that passes fine too. So the coverage of the implementation should be quite thorough, in addition to the scenarios that I could dream up for the tests targeting this new feature.

The chained transformers are created and registered using ChainedTransformationDescriptionBuilder, which is a wrapper around our existing ResourceTransformationDescriptionBuilder. At runtime, when transforming for a resource which has a chained transformer registered (or the child of such a resource), we end up in ChainedTransformingDescription which then handles the transformation chains by resolving the 'placeholders' (which are wrappers around TransformationDescriptions built up using the ResourceTransformationDescriptionBuilders) itself.

When transforming across say two version deltas, e.g. 3.0.0->2.0.0->1.0.0, the 3.0.0->2.0.0 transformation of the full resource tree happens before doing the 2.0.0->1.0.0 transformation.