Revert "Upgrade to apache-rat-plugin 0.18"

This reverts commit 7e78f98.

Author: rschmitt

pom.xml

@@ -273,7 +273,7 @@
       <plugin>
         <groupId>org.apache.rat</groupId>
         <artifactId>apache-rat-plugin</artifactId>
-        <version>0.18</version>
+        <version>0.17</version>
         <executions>
           <execution>
             <phase>verify</phase>