LUKS encryption support in Ubiquity

Alternate installer in Gutsy enables creation of encrypted partitions, however it uses dm-crypt and not cryptsetup with LUKS support. We need support for encrypted partitions in Ubiquity to create encrypted root, /home and other partitions (however /boot partition must remain unencrypted else we cannot boot the system). Dm-crypt does not allow user to change the password, but Cryptsetup with LUKS support enables use of up to seven different passphrases (or keyfiles), which can all be changed.