current groovy version/scripts not compatible with java11

[duttonw]

need to upgrade groovy scripts (also in richfaces-cdk repo) from 1.5 to 2.x compatibility

and update plugin from

<groupId>org.codehaus.groovy.maven</groupId>
<artifactId>gmaven-plugin</artifactId>

to

<groupId>org.codehaus.gmavenplus</groupId>
<artifactId>gmavenplus-plugin</artifactId>