try_login() to login users

valid_username() checks if a new username fits criteria

valid_user() checks if the user exists in the database

good_passwd() only checks for minimum password length for now.
can be later expanded to tell a user to make a stronger password.

valid_passwd() checks if the password for the specified user is correct

user_suspended() checks if the user is suspended (or not)

user_delete() deletes a user

Also:	Enforce proper usernames on account creation
	Fix bug where $SUPPORTED_LANGS needs to be reset on account creation
	Fix bug where an account could be created with an empty passwd
	Display (required) beside password fields on account creation
	Enforce good_passwd() on account creation

Signed-off-by: Loui Chang <louipc.ist@gmail.com>