Fix some warnings raised by CheckStyle

- Change ordering of 'static', 'final', etc modifiers according to
  the order suggested by JLS.

- Add comments in empty catch blocks for intentionally ignored
  exceptions.

- Add curly braces around if-else blocks.

- Move `catch` to same line as closing brace of preceding `try`
  blocks.

- Wrap long lines.

Note that this change does not fix all instances of the above errors
across the entire code base.

Change-Id: I24bb9649cc5013c249fa5d84e05322a5cdf2ace6

gerrit-server/src/main/java/com/google/gerrit/server/plugins/JarScanner.java

@@ -264,7 +264,7 @@ public class JarScanner implements PluginContentScanner {
     }
   }
 
-  private static abstract class AbstractAnnotationVisitor extends
+  private abstract static class AbstractAnnotationVisitor extends
       AnnotationVisitor {
     AbstractAnnotationVisitor() {
       super(Opcodes.ASM4);

gerrit-server/src/main/java/com/google/gerrit/server/plugins/PluginLoader.java

@@ -214,7 +214,7 @@ public class PluginLoader implements LifecycleListener {
     }
   }
 
-  synchronized private void unloadPlugin(Plugin plugin) {
+  private synchronized void unloadPlugin(Plugin plugin) {
     persistentCacheFactory.onStop(plugin);
     String name = plugin.getName();
     log.info(String.format("Unloading plugin %s", name));