Integral formulation w/ CLSVOF

[daniel.vas...@gmail.com]

Hello dear basilisk users,

I've been trying and implement the integral formulation with the CLSVOF, as it has been added to the source code of basilisk. However, I have been facing some issues. Whenever including integral.h and adapting surface tension, the correspondent time step drops to 1e-7s. The numerical case eventually diverges if the tolerance poisson is 1e-5, requiring a lower value. Attached are both codes and respective changes.