Drop description on User and Organization

[jace]

The description field on the User and Organization models is ill-defined and confusing to users. As a text field, it is also ambiguous on whether it contains plain text or HTML.

The description field should be dropped and a functionally equivalent field can be re-introduced via properties (#65).

[jace]

Counterpoint: description should not be dropped until #65 happens since the notion of public properties there isn't yet well defined. There is valuable user data in that field that shouldn't be discarded.