Check for 80-char line length limit

This is what is already written in the coding conventions; the
Checkstyle configuration was just wrong. The change required some
adjustments in FlowchardStateGermany#getNextState.

google_checks.xml

@@ -39,7 +39,7 @@
             <property name="message" value="Avoid using corresponding octal or Unicode escape."/>
         </module>
         <module name="LineLength">
-            <property name="max" value="100"/>
+            <property name="max" value="80"/>
             <property name="ignorePattern" value="^package.*|^import.*|a href|href|http://|https://|ftp://"/>
         </module>
         <module name="AvoidStarImport"/>

src/main/java/de/ddb/pdc/core/FlowChartStateGermany.java

@@ -294,13 +294,13 @@ public Question getQuestion() throws NoSuchElementException {
   @Override
   public FlowChartState getNextState(Answer answer)
       throws IllegalStateException {
-    if (this.unconditionalNextState != null) {
-      return this.unconditionalNextState.getNextState(answer);
-    } else if (this.positiveNextState != null && this.negativeNextState != null) {
+    if (unconditionalNextState != null) {
+      return unconditionalNextState.getNextState(answer);
+    } else if (positiveNextState != null && negativeNextState != null) {
       if (answer == Answer.YES) {
-        return this.positiveNextState;
+        return positiveNextState;
       } else {
-        return this.negativeNextState;
+        return negativeNextState;
       }
     }
     throw new IllegalStateException();