This function creates a composed large neighborhood. The neighborhood formed is the union of the neighborhood of nhood1 and nhood2.

The size of the neighborhood is the product of the sizes of nhood1 and nhood2.

The set of selected extractables of the union for index i is the union of the sets of selected extractables for index i1 for neighborhood n1 and for index i2 for neighborhood n2 such that i = i1*size(n2) + i2.

For any extractable, it will be restored if either nhood1 or nhood2 specify that it must be restored.