Add login to /users/:id API for current user (#13155).

Patch by Jérôme Bataille.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11437 e93f8b46-1217-0410-a6f0-8f06a7374b81
Code cleanup.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11438 e93f8b46-1217-0410-a6f0-8f06a7374b81
Removed some shoulda context.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11439 e93f8b46-1217-0410-a6f0-8f06a7374b81