ubuntuone needs to have a secure way to share with non-members

[komputes]

Use case:
-Want to privately share many many pictures with family

ubuntuone should have a a way to share with non-members and non-ubuntu users securely. This could mean the ability to create password protected public share (https accessible to anyone with a share password + URL). This could also mean that external users should be able to register for accounts from the ubuntu-one website and not just the client.