Incorporate user-registration on startup

[kasper]

We are launching a new website for DataCleaner soon and in order to build the community we want users to be more aware of the online activities through user-registration, mailing list subscription etc.

This ticket includes the construction of a registration dialog in the DataCleaner GUI application. The dialog should let people create a profile, use an existing profile or not use a profile (which will cause the dialog to keep showing up every time the app. starts).

[kasper]

Fixed as of rev. [718].

[kasper]

Added rev. [722] which implements the htpasswd hashing algorithm so that we don't expose the raw password in the HTTP requests :)