Update checkstyle.xml

Think this should fix a load of our new warnings.

checkstyle.xml

@@ -91,7 +91,7 @@
                      value="Local variable name ''{0}'' must match pattern ''{1}''."/>
         </module>
         <module name="ClassTypeParameterName">
-            <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)"/>
+            <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9][_]*[T]$)"/>
             <message key="name.invalidPattern"
                      value="Class type name ''{0}'' must match pattern ''{1}''."/>
         </module>
@@ -133,4 +133,4 @@
         </module>
         <module name="CommentsIndentation"/>
     </module>
-</module>
+</module>