[7.x][JBMETA-382] Support nested expressions and recursive resolution

Also fixes https://issues.jboss.org/browse/JBMETA-381 and JBMETA's equivalent to https://issues.jboss.org/browse/DMR-15 (sorry, no JBMETA JIRA for that one.)

This is needed for https://issues.jboss.org/browse/EAP6-320

This bumps the version to 7.2.0. As the 7.x branch is used in EAP 6.3, with 7.1.x being the minor stream, we should not include this change in a 7.1.x micro and need a new minor stream for EAP 6.4. This change is too large for inclusion in any EAP 6.3 CP.