Cleanup implementation of REST views

- specify return type if possible
- remove unnecessary throw declarations
- convert some of the thrown exceptions to RestExceptions
- do not throw Exception but specific exceptions
- sort throw declarations (first RestExceptions, then other
  exceptions)

Having explicit return types and exceptions makes it easier to
programatically invoke the REST views, e.g. if a plugin wants to add a
REST view that wraps a Gerrit core REST view.

Change-Id: I5c59553b6cfad457f7ec037cceb08936247bf8e8
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>

gerrit-server/src/main/java/com/google/gerrit/server/change/GetTopic.java

@@ -16,11 +16,10 @@ package com.google.gerrit.server.change;
 
 import com.google.common.base.Strings;
 import com.google.gerrit.extensions.restapi.RestReadView;
-import com.google.gwtorm.server.OrmException;
 
 class GetTopic implements RestReadView<ChangeResource> {
   @Override
-  public Object apply(ChangeResource rsrc) throws OrmException {
+  public String apply(ChangeResource rsrc) {
     return Strings.nullToEmpty(rsrc.getChange().getTopic());
   }
 }