v3: CutFEm for FSI

todo:

• smoother extension of w
• unstable solution for large viscosity difference (10^4) -> look at cut_weights
• dual problem for prescribed solid
• alternative formulation: (grad(p),v) instead of (p, div(v))
• linear solver convergence for Q2/Q1
• alternative ghost penalization -> Direct Penalty
• Level Set functionality
• FSI with Translation - Deformation split
• no convergence for RT elements