Make EmailArguments public to allow sending mails from plugins

With this minor change plugins would be able to send emails using Gerrit
internal API.

Change-Id: I289a7585a1090f281a0d4721ac13fb6ee12af2a4
Signed-off-by: Dariusz Luksza <dariusz@luksza.org>

gerrit-server/src/main/java/com/google/gerrit/server/mail/EmailArguments.java

@@ -42,7 +42,7 @@ import org.apache.velocity.runtime.RuntimeInstance;
 
 import java.util.List;
 
-class EmailArguments {
+public class EmailArguments {
   final GitRepositoryManager server;
   final ProjectCache projectCache;
   final GroupBackend groupBackend;