Save mesh

[keiyamamo]

For the post-processing, we work a lot with mesh (fluid only mesh / solid only mesh / refined version of those two). Thus, I think it would make sense that turtleFSI produce a folder called Mesh and we can do post-processing within the result folder. Please let me know if you have any thoughts.

[johannesring]

I am fine with this change, although I am not sure if it should be here in turtle or in fsipy/the problem file.

[keiyamamo]

@johannesring Good point, but I also don’t see negative side of having it in turtle. I will merge this for now, but we can always revert back and transfer the this to be inside fsipy/problem file :)