[mod:php, ctp] Add reset forgotten password feature.

Add the reset password feature by adding the forgot_password.ctp view
to the Users views and Adding the relevent functionality to the
UsersController.
[mod:php, ctp] Finish reset password functionality

Finish reset password functionality by modifying the forgotPassword() to
set a new password and send the password to the user using a responsive
HTML email. Created the HTML email, modified the UsersController and
refactored the SendEmail class to better handle dynamic email content.