Turn on many more Eclipse warnings, and fix them

- Warn on empty statements, e.g. "for (;;);". These may be
   typos and are easily replaced by "for (;;) {}" which is more
   explicit.
 - Warn on field hiding. This allows cleanup of many acceptance test
   members, at the cost of a couple of renames and the occasional
   suppression (when the field is in a public nested enum that shadows
   a public constant).
 - Warn on unnecessary casts.
 - Warn on unused declared thrown exceptions. In addition to reducing
   method signature length and number of imports, this also eliminated
   some impossible catch blocks.
 - Warn on missing @Override annotations.
 - Warn on unused parameters. This is likely the most controversial,
   as a few relatively common patterns require unused parameters in a
   way that Eclipse can't ignore. However, it also resulted in cleanup
   of a lot of unnecessary injections and method parameters, so I
   think the cost was worth it.

Change-Id: I7224be8b1c798613a127c88507e8cce400679e5d

gerrit-util-ssl/src/main/java/com/google/gerrit/util/ssl/BlindSSLSocketFactory.java

@@ -34,13 +34,16 @@ public class BlindSSLSocketFactory extends SSLSocketFactory {
 
   static {
     final X509TrustManager dummyTrustManager = new X509TrustManager() {
+      @Override
       public X509Certificate[] getAcceptedIssuers() {
         return null;
       }
 
+      @Override
       public void checkClientTrusted(X509Certificate[] chain, String authType) {
       }
 
+      @Override
       public void checkServerTrusted(X509Certificate[] chain, String authType) {
       }
     };