Formulation::setRHS() and co.

Hi everyone,

I have a few suggestions for additional methods. I didn't know the cleanest way to proceed, so I just went with many MRs... Feel free to let me know of a better/cleaner/more official/... way if needed ;).

So let's start with the first one!

I would like to alter the right-hand-side (RHS) of a Formulation matrix. I thus propose to add something like Formulation::setRHS() and Formulation::setRHSBlock(). Regarding the 'block' version, I had to implement a 'partial' VectorFactory::setToZero().

Does this sound legit? Is there perhaps a better/cleaner way of altering a RHS with the existing api?

Cheers, Nicolas.