basic feature pack & server build through maven plugins

The plugins should be ready to replace wildfly-build-maven-plugin in both Wildfly and Wildfly Core, my branches pass all tests locally.

WildFly Core: https://github.com/emmartins/wildfly-core/tree/wildfly-build-tools
WildFly: https://github.com/emmartins/wildfly/tree/wildfly-build-tools-2

Some loose notes:
- that WildFly branch is on top of #6514
- I kept the wildcard maven exclusions for now, ctomc said the issue with it is that it doesn't play nice with big projects, dunno if wildfly-feature-pack is not big enough, but so far I saw no issue. I can remove these next week, but I think it will be very painful to maintain. 
- Not sure if the javadoc executions are at the right poms, or if anything else needs to be changed wrt dist release