Use Galleon to build WildFly full distributions

Switch from the current feature-pack-based provisioning to Galleon and WildFly Galleon plugins.
Create galleon feature packs as Maven artifacts and use them to produce the thin and fat servlet, full and other testsuite distributions.
The legacy servlet and full feature-packs should still be built. They could still be used to produce the legacy builds and distributions by activating Maven profiles.