Makes some attributes optional in API response to get faster/lightweight responses.

These attributes are not required for common uses case (eg. updating an object). They can be requested in the reponse using the 'include' parameter. Example GET /issues/1.xml?include=journals. The list of attributes that can be included in responses will be documented in the wiki.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@4486 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/views/users/show.api.rsb

@@ -20,5 +20,5 @@ api.user do
         end
       end if membership.project
     end
-  end if @memberships.present?
+  end if include_in_api_response?('memberships') && @memberships
 end