Update model/classes/filter.class.php

The original filter class filters out "-", and replace it with "".
Revert "Update model/classes/filter.class.php"

This reverts commit af81ae48637fb2651b7f63ed82d99ff115cabbc7.
Update model/classes/filter.class.php

The original filter class filters out "-", and replace it with "".
Adding username filter in filter class

To fix the bug of usernames with hyphen, a username filter is created.
Incorrect use of filter in task.process.php was fixed.
Register.process.php is aligned with the new change. Other files
concerning with username have functioning AJAX auto matching, which are
not changed.
Adding Username Filter in filter class

To shot the problem of assigning a task leader whose username has a
hyphen, and to avoid any possible damage to the existing filter
(alphanum). A username filter is added, and task.process and
register.process are changed accordingly.
Merge pull request #37 from kluther/Chloe