Default data loader raises an error when called from the rake task (#14607).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@12076 e93f8b46-1217-0410-a6f0-8f06a7374b81
Moved CUSTOM_FIELDS_TABS out of the model.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@12077 e93f8b46-1217-0410-a6f0-8f06a7374b81