decoupled ade-xjc version from citygml4j version

build.gradle

@@ -6,7 +6,7 @@ plugins {
 }
 
 group 'org.citygml4j'
-version '2.8.1'
+version '2.8.2'
 
 sourceCompatibility = 1.8
 mainClassName = 'org.citygml4j.ade_xjc.ADESchemaCompiler'
@@ -16,6 +16,7 @@ repositories {
 }
 
 ext {
+    citygml4jVersion = '2.9.0'
     date = new Date()
 }
 
@@ -28,6 +29,7 @@ jar {
     manifest {
         attributes('Implementation-Title': project.name,
                 'Implementation-Version': project.version,
+                'Specification-Version': citygml4jVersion,
                 'Main-Class': mainClassName)
     }
     into('META-INF') {

src/main/java/org/citygml4j/ade_xjc/ADESchemaCompiler.java

@@ -111,7 +111,7 @@ public class ADESchemaCompiler {
 
 		if (version) {
 			System.out.println(getClass().getPackage().getImplementationTitle() + " version " + getClass().getPackage().getImplementationVersion());
-			System.out.println("XML Schema binding compiler for CityGML ADEs; use with citygml4j version " + getClass().getPackage().getImplementationVersion());
+			System.out.println("XML Schema binding compiler for CityGML ADEs; use with citygml4j version " + getClass().getPackage().getSpecificationVersion());
 			System.exit(0);
 		}