#38 concatenation/collapsing of relationships

[Rob Lintern]

Add support for configuring simple concatenation of
relationships;

From Benard Chabot:

| > | > Another second need is to be able to define
kinds
| of "virtual"
| > | > relations :
| > | > For example :
| > | > - A is link to B by a X
relation type
| > | > - B is link to C by a Y
relation type
| > | > - B is link to D by a Y
relation type
| > | >
| > | > I want to be able to define a graphic view
were I can
| > | follow the X
| > | > relation type and after (i.e. in the
same "virtual"
| > | hierarchie) the Y
| > | > relation type ...
| > | > ... And/Or to be able to define Z relation
type
| which is the
| > | > *concatenation*
| > | > of the X relation type and the Y relation
type => so I
| > | have A linked
| > | > to C and D by a Z relation type
| > | >
| > | > The idea is to be able to define *views* in
which you
| > | can browse one
| > | > relation or two or more concatenated
relations ...