linearized scheme and D b.c. in outer loops like Uzawa

• make the linearized.hh scheme work again (including python bindings)
• allow for setup() without argument to linearize around zero
• replace rhs argument to solve with named argument rightHandSide which correctly handles the right hand side vector together with DirichletBC

Description

Given a scheme with dirichlet boundary conditions g then calling scheme.solve(target,rhs) always returns target=g an the boundary. Calling scheme(u,w)returnsw=u-gon the boundary so the correct behavior fir thesolvemethod is to returntarget=rhs+gon the boundary. This is now done when callingsolvewith the named argumentrightHandSide. The original version with rhs` argument is deprecated. The original behavior can be reproduced by calling

scheme.setConstraints(0,rhs)
scheme.solve(target=target,rightHandSide=rhs)