Themes: Add versioning to the theme feature

As new features and enhancements to the theme apk format are added
we will need a way for themes to specify which version of the theme
format they are targeting.  Exclusion of the theme feature in a
theme apk will imply v1.

Change-Id: I0016d58341ca3144bb4a4faa16663ab29439ab24

config/permissions/org.cyanogenmod.theme.xml

@@ -15,5 +15,14 @@
 -->
 
 <permissions>
+    <!-- The features listed here should coincide with the various iterations of
+         the CyanogenMod theme engine.  New org.cyanogenmod.theme.vX features
+         should only be added when the structure of the theme apk format is changed
+     -->
+
+    <!-- This is an alias for org.cyanogenmod.theme.v1 -->
     <feature name="org.cyanogenmod.theme" />
+
+    <!-- Supports themes using v1 of the theme engine -->
+    <feature name="org.cyanogenmod.theme.v1" />
 </permissions>