Generate "modern" java to reduce warnings

* @SuppressWarnings("hiding") for field names that are reused in inner
  classes.
* @Override for methods defined in com.google.protobuf.micro.MessageMicro
* Removed unnecessary type casting
* Only throw exception from writeTo when there are fields to write.

This removes over 1,000 warnings from the Play client.

Change-Id: I9049c94f1e6aec5e5547898defc03c8d379c3c10
1 file changed