Add option to force a user to change password on next login

* Add force_password_reset field to user

* Add force_password_reset field to user edit form
  Also, reindent the form HTML.

* Rename force_password_reset to force_password_change

* Force password change: Show form on login, allow change

* Remove unused step definitions for setting RAILS_ENV

* Fix forced password change, add cuke

* Don't reveal whether user exists when not authenticated

* Also add spec for testing reaction when user is not allowed to change the password.

* Improve force password change code after review

* Fix MyController password test and change to spec

* Fix AccountController force password change spec