[om-list] use case list: 2nd try

[Mark Butler]

Hello everybody,

For user interface purposes, we should add separate use cases for "create
relationship", "edit relationship", "move relationship", and "delete
relationship". 
Internally, a property and a relationship are actually the same thing, but
making the distinction on the user interface level makes life much easier for
users who do not want to consider that abstractions like "height", "weight",
and "color" are relationships to or between full blown entities.  Traditional
data modelling makes a distinction between the latter, which is called a
"domain" and the former, which is called an "entity".