optional namespace/package reference in generated Octave code

[mfrigerio17]

When the generated code references some other generated functions, e.g. an IK solver calling the FK solver.

To allow the user to put the generated code in a matlab namespace (a "plus folder"), it should be possible to configure the namespace name to be used in the generated code to call other generated functions.

So as to generate e.g. ns.myFKSolver(... rather than myFKSolver(...