CMSDK: Hide CMContextConstants from docs.

Until we can reference these managers through the current context,
  we should hide the constants that are utilized to retrieve them.
  Current implementations should stick to the singleton getInstance
  pattern.

Change-Id: I6c084a3a5b0745b0b6c5d10e000a40f5e61117ea

src/java/cyanogenmod/app/CMContextConstants.java

@@ -17,10 +17,10 @@
 package cyanogenmod.app;
 
 /**
- * Constants to be used with {@link android.content.Context#getSystemService}
- * to retrieve published system services
+ * @hide
+ * TODO: We need to somehow make these managers accessible via getSystemService
  */
-public class CMContextConstants {
+public final class CMContextConstants {
 
     /**
      * @hide