Don't force public variables to use Hungarian notation (#8774)

People generally have expressed a dislike for the Hungarian notation
used in member variables, especially in examples/templates, and our
styleguide shouldn't be forced on downstream consumers, so this removes
all Hungarian notation from the examples/templates.

There are _some_ benefits to Hungarian for private member variables
(like knowing what's a member vs. local in a PR review) so we'll keep
private member variables the same for now, but public variables should
no longer use Hungarian notation, since it looks much worse. A new PMD
XPath rule has been added to accomplish this goal. Some other
non-compliant variables were fixed for the new rule.

styleguide/pmd-ruleset.xml

@@ -12,7 +12,7 @@
   <exclude-pattern>.*/Timestamped.*\.java</exclude-pattern>
   <exclude-pattern>.*/units/measure/.*\.java</exclude-pattern>
 
-  <exclude-pattern>.*/*IntegrationTests.*</exclude-pattern>
+  <exclude-pattern>.*/*Examples.*</exclude-pattern>
   <exclude-pattern>.*/*JNI.*</exclude-pattern>
   <exclude-pattern>.*/math/proto.*</exclude-pattern>
   <exclude-pattern>.*/command3/proto.*</exclude-pattern>
@@ -143,4 +143,22 @@
             ]]>
     </example>
   </rule>
+  <rule name="PublicFieldNamingConvention"
+        language="java"
+        message="Public fields must follow lowerCamelCase."
+        class="net.sourceforge.pmd.lang.rule.xpath.XPathRule">
+    <description>
+
+    </description>
+    <priority>3</priority>
+    <properties>
+      <property name="xpath">
+        <value>
+  <![CDATA[
+  //ClassDeclaration[not(matches(@PackageName, "org.wpilib.math"))]/ClassBody/FieldDeclaration[@Visibility = 'public' and @Static = false()]/VariableDeclarator[not(matches(@Name, "^[a-z][a-zA-Z0-9]*$"))]
+  ]]>
+        </value>
+      </property>
+    </properties>
+  </rule>
 </ruleset>