A DSDE coordinator should be placed as root of model hierarchy if appropriate

[RomainFranceschini]

Currently, the direct connection phase, which consist in removing intermediate coupled models from the hierarchy and adjusting couplings accordingly treats dynamic coupled models as coupled models.

If a dynamic coupled model is present in the hierarchy, a similar model should be placed as root of the transformed hierarchy, so that the appropriate coordinator is used.

Though, if several DSDEs are present in the hierarchy, they should be leaved untouched, in order to prevent several executives to exist within a common coupled.