[3.3] Implementing bcrypt for password hashing into Joomla as default method

This PR changes the Joomla password hashing infrastructure to using the password_hash() method and thus bcrypt for hashing the password.

I tested this code with PHPass passwords, bcrypt passwords and MD5 passwords with and without salt. All passwords are correctly changed to bcrypt and login is working. You also get an error when you use the wrong password.