Document alias modules as deprecated or private in their module.xml

Include a standard comment in the module.xml for module-alias modules noting that the alias is deprecated or private. Which to use depends on the status of the target module – deprecated for public targets, private for private targets.

Use consistent comment language that can be grepped for.

An alias module cannot have its own jboss.api property setting, so all we can do is add comments.

For public targets, the alias is deprecated because we want people to use the target, not the alias. Same applies with private targets, but there we don't want people using the alias at all.