Correcting issue with autogenerated binding

Adding a partial class declaration to handle implementing
Java.Lang.IComparable.

See section 4 in
http://docs.xamarin.com/guides/android/advanced_topics/java_integration_overview/binding_a_java_library_%28.jar%29
for details.

See also
http://forums.xamarin.com/discussion/1950/binding-jar-file-with-class-that-implements-java-lang-icomparable