[WFLY-490] RBAC for standalone servers

First merge of RBAC work to master.

This focuses on securing the central( (i.e. non-JMX) management API for standalone servers. RBAC in a managed domain will not work with the commits in this PR. There's some configuration stuff related to managed domain here, but it's not actually tied into running services.

RBAC for JMX is not complete in this PR; that will be completed in later PRs. JMX behavior is currently as follows when rbac is enabled:

1) A JMX user with a Local connection gets SuperUser privileges.
2) A JMX user with a remote connection who calls into the jboss.as JMX domains will have permission checks enforced the same as if he or she was using a non-JMX interface. However, no particular effort has been made to adapt the JMX responses to any failures that may occur due to lack of access.
3)A JMX user with a remote connection who calls into the mbean not in the jboss.as JMX domains will have full privileges.