Refactor cumadopt and adopt

[gvegayon]

Both of these matrices should allow for other values. Currently, we have:

• adopt: marks one on the time of adoption, and zero otherwise.
• cumadopt: marks one starting the time of adoption.

What we want is to allow:

• adopt to have -1 to mark disadoption.
• cumadopt to have the capability of showing periods of time during which the agents have adopted, allowing for zero value when there's no adoption.

Furthermore, these should be arrays so that the third dimension marks the behavior.

Other considerations:

• The printdiffnet method should allow to show more than one behavior
• Summary diffnet do the same thing.
• Eventually (not now) this will require refactoring the plot figures, which currently support a single behavior.