Change the revision property for the add-ons from "version" to "revision".

"version" will still be supported by tools for the moment. But all add-ons
must move to "revision" asap.
diff --git a/sdk_addon/manifest.ini b/sdk_addon/manifest.ini
index fda2a84..3c5b2a5 100644
--- a/sdk_addon/manifest.ini
+++ b/sdk_addon/manifest.ini
@@ -7,8 +7,8 @@
 # version of the Android platform on which this add-on is built.
 api=3
 
-# version of the add-on
-version=1
+# revision of the add-on
+revision=1
 
 # list of libraries, separated by a semi-colon.
 libraries=com.example.android.platform_library