Fixes #3334, redesigned the reset password functionality.

Notes:
  * Resetting password is done through AJAX and the reset token does not need to be entered in a form.
  * Moved password related utility functions in UsersManager_API to UsersManager as static functions.
  * Added hidden _isPasswordHashed parameter to UsersManager::updateUser.
  * Make sure superuser login is set in Access instance when setSuperUser(true) is used.
  * Add ability to get rendered form data as array in QuickForm2 (moved existing logic in Piwik_View into new function).


git-svn-id: http://dev.piwik.org/svn/trunk@6900 59fd770c-687e-43c8-a1e3-f5a4ff64c105