Execute CLI commands in a new process

CLI commands are executed in the same process maven is running in. In WildFly Core CLI has the option to run an embedded server. When the CLI high level commands are initialized it also initializes org.jboss.modules.Module which has some initialization for JAXP. Because of the way JAXP works problems can occur if another version of JAXP was initialized first in the maven process. This leads to the execute-commands goal failing if another plugin is executed first. See WFMP-48 for some details there.

This would also potentially solve WFMP-11 as we could use a real modular environment. We could also allow the embedded server to be used to actually configure a container as well.

One of the issues is going to be processing stdout results. We may need the process to use specific return codes to indicate errors and only read stdout or stderr if an unsuccessful return code was found for the process.