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/account/CreateEmail.java

@@ -78,8 +78,8 @@ public class CreateEmail implements RestModifyView<AccountResource, Input> {
   }
 
   @Override
-  public Object apply(AccountResource rsrc, Input input) throws AuthException,
-      BadRequestException, ResourceConflictException,
+  public Response<EmailInfo> apply(AccountResource rsrc, Input input)
+      throws AuthException, BadRequestException, ResourceConflictException,
       ResourceNotFoundException, OrmException, EmailException,
       MethodNotAllowedException {
     if (self.get() != rsrc.getUser()