applied RM 2.x compatibility patch as provided by darksoul42 in issue #18
- Fixed autoregistration and enabled manual login

Continued fixing minor issues brought up on issue #18.
- Self-Registration form is working (although it is not used by my installations)
- Logout now returns to login screen allowing the user to change identity
- Locked users cannot log in
Merge pull request #1 from ma-ku/redmine_2x_compat

- Fixed autoregistration and enabled manual login
Fix found from Mark Draheim: http://mark.diatonic.de/linux/redmine-http-auth-plugin-fix