Break close association of AppclientXml with WildFly-Core

AppClientXml is written on the basis that it is in the same project as the remaining domain management parsers, as an example it is dependent on calling certain version specific vault methods.

Changes will also be needed to wildfly-core but any access to parsers in wildfly-core should be switched to agreed entry points that will be maintained by compatibility.

As an example this block: -

        if (element == Element.VAULT) {
            switch (namespace) {
                //Less than 1.1 does not end up in this method
                case DOMAIN_1_1:
                case DOMAIN_1_2:
                case DOMAIN_1_3:
                case DOMAIN_1_4:
                case DOMAIN_1_5:
                case DOMAIN_2_0:
                case DOMAIN_2_1: {
                    parseVault_1_1(reader, address, namespace, list);
                    break;
                }
                default: {
                    parseVault_3_0(reader, address, namespace, list);
                }
            }

Should be replaced with a call to parseVault(), the parseVault() method will then be responsible for identifying the correct version.

Changes should also be made to AppClientXml to make it compatible with multiple major versions in use concurrently for jboss-as-config - otherwise this class is seriously likely to be missed again for all further updates.