migrate some basic strong password randomizing stuff
adjust users_controller to use random_password facilities, migrated from strong_passwords
User edit: Improve JavaScript and form

[ci skip]
User: Always force password change on random password assignment
Improve form and process random password assignment
User form: Fix random password assignment checkbox
Add cuke for testing random password assignment
User spec: check force password change after random password assignment
Fix mail handler test failing after forced password change
Add changelog entry

[ci skip]
UsersController: improve random password control flow; cleanup

The removed methods are unused.
Small fixes after code review
Merge pull request #239 from opf/feature/rails3_random_password

Feature/rails3 random password