Enable PMD rule UnnecessaryReturn and fix violations

brouter-core/src/main/java/btools/router/OsmNogoPolygon.java

@@ -132,7 +132,6 @@ public class OsmNogoPolygon extends OsmNodeNamed {
     ilon = cx;
     ilat = cy;
     radius = rad * 1.001 + 1.0; // ensure the outside-of-enclosing-circle test in RoutingContext.calcDistance() is not passed by segments ending very close to the radius due to limited numerical precision
-    return;
   }
 
   /**

brouter-server/src/main/java/btools/server/SuspectManager.java

@@ -543,7 +543,6 @@ public class SuspectManager extends Thread {
     }
     bw.write("</body></html>\n");
     bw.flush();
-    return;
   }
 
 

brouter-util/src/main/java/btools/util/ByteDataWriter.java

@@ -142,7 +142,6 @@ public class ByteDataWriter extends ByteDataReader {
     ab[aboffset++] = (byte) (i7 | 0x80);
 
     ab[aboffset++] = (byte) (v);
-    return;
   }
 
   public int size() {

config/pmd/pmd-ruleset.xml

@@ -39,7 +39,6 @@
         <exclude name="UncommentedEmptyMethodBody" />
         <exclude name="UnnecessaryFullyQualifiedName" />
         <exclude name="UnnecessaryModifier" />
-        <exclude name="UnnecessaryReturn" />
         <exclude name="UnusedFormalParameter" />
         <exclude name="UnusedLocalVariable" />
         <exclude name="UnusedPrivateField" />