interface "a la JuMP" with macros

[trigaut]

We figured out with Frapac that it might be clever to create an interface similar to the JuMP one using macros:

@addStateVariable
@AddControl
@addDynamics
@addConstraints....

what do you think?

[leclere]

Yes that would be nice, it goes along the idea of having an interface that allow easy construction of the problem.