Clean up use of jboss.as.release.version

Our poms have a 'jboss.as.release.version' property that is used for two distinct purposes:

1) In the root pom it drives the value of the JBossAS-Release-Version property in our MANIFEST.mf files.

2) In many places throughout the poms its value is appended to the value of the server.output.dir.prefix property to produce the names of various output dirs used in the build.

This is a bit messy, and is made messier because in the EAP variant of the poms, nearly all[1] of the type 2) uses have been converted to a different property, named 'jboss.eap.release.version'. EAP then changes the value of this to a short form version (e.g. "7.1") rather than the full maven GAV version. However, this property name is not appropriate for upstream. The effect of this is it's unnecessarily difficult to go from a WF tag to an EAP branch.

To clean this up I propose to do the following:

A) Replace all the type 2) uses of jboss.as.release.version in the poms with a new property, "server.output.dir.version". This better describes the purpose of the property and has a name that is agnostic between WildFly and EAP.

B) Examine some uses of "jboss.eap.release.version" in EAP that are not present in WF and if appropriate port them to WF, but using "server.output.dir.version".

C) Either drop jboss.as.release.version for the type 1) manifest use, and directly use "project.version" (which is the only value ever provided for this), or better comment the declaration of jboss.as.release.version so its sole intended use is clear. (Probably for now I'll do the latter to avoid risk of unintended side effects.)

[1] "Nearly all" because there's still this, which I think should be corrected to use the same version string as the others:

<wildfly.web.build.output.dir>servlet-dist/target/${server.output.dir.prefix}-servlet-${jboss.as.release.version}</wildfly.web.build.output.dir>