Use project.parent.version for taverna.engine

avoids error with mvn release:prepare

    [ERROR] Failed to execute goal org.apache.maven.plugins:maven-release-plugin:2.5.2:prepare (default-cli) on project apache-taverna-engine: The artifact (org.apache.taverna.engine:taverna-workflowmodel-api) requires a different version (3.1.0-incubating) than what is found (${project.parent.version}) for the expression (taverna.engine.version) in the project (org.apache.taverna.engine:taverna-activity-archetype). -> [Help 1]
diff --git a/taverna-activity-archetype/pom.xml b/taverna-activity-archetype/pom.xml
index 3cd7e47..916a027 100644
--- a/taverna-activity-archetype/pom.xml
+++ b/taverna-activity-archetype/pom.xml
@@ -30,9 +30,6 @@
     <description>Archetype to build a Taverna 3 service activity.
     Includes engine and UI parts, and a test class to run the workbench with the new activity.
     </description>
-    <properties>
-      <taverna.engine.version>${project.parent.version}</taverna.engine.version>
-    </properties>
     <build>
           <resources>
               <resource>
@@ -91,25 +88,25 @@
       <dependency>
         <groupId>org.apache.taverna.engine</groupId>
         <artifactId>taverna-workflowmodel-api</artifactId>
-        <version>${taverna.engine.version}</version>
+        <version>${project.parent.version}</version>
         <scope>test</scope>
       </dependency>
       <dependency>
         <groupId>org.apache.taverna.engine</groupId>
         <artifactId>taverna-reference-api</artifactId>
-        <version>${taverna.engine.version}</version>
+        <version>${project.parent.version}</version>
         <scope>test</scope>
       </dependency>
       <dependency>
         <groupId>org.apache.taverna.engine</groupId>
         <artifactId>taverna-workflowmodel-impl</artifactId>
-        <version>${taverna.engine.version}</version>
+        <version>${project.parent.version}</version>
         <scope>test</scope>
       </dependency>
       <dependency>
         <groupId>org.apache.taverna.engine</groupId>
         <artifactId>taverna-activity-test-utils</artifactId>
-        <version>${taverna.engine.version}</version>
+        <version>${project.parent.version}</version>
         <scope>test</scope>
       </dependency>
 
diff --git a/taverna-activity-archetype/src/main/resources/archetype-resources/pom.xml b/taverna-activity-archetype/src/main/resources/archetype-resources/pom.xml
index cd6e6cd..8e54ab3 100644
--- a/taverna-activity-archetype/src/main/resources/archetype-resources/pom.xml
+++ b/taverna-activity-archetype/src/main/resources/archetype-resources/pom.xml
@@ -32,9 +32,9 @@
 	## The ${} below are expanded from taverna-engine pom.xml
 	## by resource filtering, rather than by Velocity
 	## http://maven.apache.org/plugins/maven-resources-plugin/examples/filter.html
+            <taverna.engine.version>${project.parent.version}</taverna.engine.version>
             <taverna.language.version>${taverna.language.version}</taverna.language.version>
             <taverna.osgi.version>${taverna.osgi.version}</taverna.osgi.version>
-            <taverna.engine.version>${taverna.engine.version}</taverna.engine.version>
             <taverna.workbench.version>3.1.0-incubating-SNAPSHOT</taverna.workbench.version>
 	</properties>