Add unique index on custom_fields_trackers (#13059).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11329 e93f8b46-1217-0410-a6f0-8f06a7374b81
Add unique index on custom_fields_projects.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11330 e93f8b46-1217-0410-a6f0-8f06a7374b81
Fixed: Can't clear custom field value through context menu in the issue list (#13075).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11331 e93f8b46-1217-0410-a6f0-8f06a7374b81