Upgrade to 18-RC1

Author: jericks

pom.xml

@@ -467,7 +467,7 @@
         </plugins>
     </reporting>
     <properties>
-        <gt.version>18-SNAPSHOT</gt.version>
+        <gt.version>18-RC1</gt.version>
     </properties>
     <name>geoscript groovy</name>
     <description>A groovy implementation of geoscript.</description>