Preload issue authors when displayed on the issue list (#16091).

git-svn-id: http://svn.redmine.org/redmine/trunk@12911 e93f8b46-1217-0410-a6f0-8f06a7374b81
Preload authors for /issues API calls.

git-svn-id: http://svn.redmine.org/redmine/trunk@12912 e93f8b46-1217-0410-a6f0-8f06a7374b81
Prevent N queries on custom_fields when call /issues API.

git-svn-id: http://svn.redmine.org/redmine/trunk@12913 e93f8b46-1217-0410-a6f0-8f06a7374b81