Missing notation for relation entities that are the domain/range of some other relation entity.

[NicolasRouquette]

Here is an example:

concept A

concept B

relation entity C [
  from A
  to B
  forward c
]

concept D

relation entity E [
  from C
  to D
  forward e
]

With Rosetta 1.0.6, the above produces a diagram like this:

This diagram is incomplete as it lacks relation entity E. More specifically, relation entity C should be displayed as a box instead of a line so that it should be the source/target of other relation entities like E.