#4 format of .sof

I think there is a design-bug about format of SofaaLink
in .sof files:

For each link, we need to know a 2-uple of such infos:
<for interface = "id1", the other bound of the vector is
located at x= y= >

Note that we don't really need to know which interfaces
are associated to this link (as it is already in xADL file)
but we need to associate an interface to a location of
the other bound of the vector, and not only 4
independant points.

So we must change the format of sof files and add
Some methods must also be add to SofaaLink,
something like:
SetVectorDirection(String interfaceId, Point otherBound);