Changes in samples build scripts

- Adding devmode task to all ant samples with the option to run
  the classic model adding gwt.args=-nosuperDevMode
- Detect whether the example is a maven build, and notice
  the user about it.
- Upgrade mobilewebapp gae version

Change-Id: I4061ea6d2d699bcb8ab437f1b60e3ff0c08cd3f2
diff --git a/samples/build.xml b/samples/build.xml
index 36d6703..1511036 100644
--- a/samples/build.xml
+++ b/samples/build.xml
@@ -11,7 +11,7 @@
   </target>
 
   <target name="dynatablerf" description="Build dynatablerf">
-    <gwt.ant dir="dynatablerf" target="source" />
+    <gwt.ant dir="dynatablerf" />
   </target>
 
   <target name="hello" description="Build hello">
@@ -27,7 +27,7 @@
   </target>
 
   <target name="mobilewebapp" description="Build mobile web app">
-    <gwt.ant dir="mobilewebapp" target="source" />
+    <gwt.ant dir="mobilewebapp" />
   </target>
 
   <target name="showcase" description="Build showcase">
@@ -35,7 +35,7 @@
   </target>
 
   <target name="validation" description="Build validation">
-    <gwt.ant dir="validation" target="source" />
+    <gwt.ant dir="validation" />
   </target>
 
   <target name="validationtck" description="Build validation TCK">