Fix Issue With Garbage Collection

[gtjusila]

This fix the issue mentioned in #296.

When creating a model using JuMP, i.e. via model = Model(SCIP.Optimizer). JuMP creates a model with Caching + Constraint Bridge activated. The way this works is during the optimize! call JuMP will call the MOI.empty! function which first delete the existing SCIPData object, creates a new on, then reinput all the problem in one go. This means that the SCIPData that was created during the Model(SCIP.Optimizer) call and the one that is used during the optimization process may differ.

In the pull request #290, the finalizer was only added to the SCIPData created during the Model call. Now the finalizer call is also added to the SCIPData object created during the MOI.empty! call.