iFunc: create a linkdata method

[farhi]

Create a linkdata method:

• linkdata(model, fig/handle)

when no fig/handle, a new plot figure is created, as well as a uitable for parameters.
The model should have a new Handle(s) property.
The handle can also be a uitable, to link with a Parameter Window, which must then store a handle to the original model.

The plot will be updated when:

• new feval
• new parameter value, which should trigger a new feval
• new Constraint, which should trigger a new feval

The uitable can be modified, and then the model follows. This then triggers refresh of any links plot.
The model can be modified and then the uitable and plot follow.

The plot update must be executed only after a given time when the object has not been modified in between (to avoid many parameter updates which would all trigger a new plot/feval).

• linkdata(model, [])

should remove links.

[farhi]

This depends on #184 to allow 'soft' links