Move GWT source out of src/main/java.

Also updated maven-compiler-plugin to newer less crack-smokey version.

pom.xml

@@ -58,23 +58,29 @@
           <exclude>pythagoras/util/Platform.java</exclude>
         </excludes>
       </resource>
+      <resource>
+        <directory>${basedir}/src/gwt/java</directory>
+        <includes>
+          <include>**/*.java</include>
+        </includes>
+      </resource>
     </resources>
     <plugins>
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-compiler-plugin</artifactId>
-        <version>2.3.2</version>
+        <version>3.1</version>
         <configuration>
           <source>1.6</source>
           <target>1.6</target>
           <fork>true</fork>
           <showDeprecation>true</showDeprecation>
           <showWarnings>true</showWarnings>
-          <!-- yes, this is apparently the Right Way to do this -->
+          <compilerArgs>
-          <compilerArgument>-Xlint" "-Xlint:-serial" "-Xlint:-path</compilerArgument>
+            <arg>-Xlint</arg>
-          <excludes>
+            <arg>-Xlint:-serial</arg>
-            <exclude>pythagoras/gwt/**</exclude>
+            <arg>-Xlint:-path</arg>
-          </excludes>
+          </compilerArgs>
         </configuration>
       </plugin>
       <plugin>