Tanhmesh

Hi Chi-Tuan

Hereby the development to have the mesh stretching as in GOTM, as discussed by email.

It included a short section for the manual as well as a test case.

I did a rebase main. However after doing so, I see **[Fix **** #971 (closed)**] Spherical coordinates in TELEMAC-3D also included here. I did not expect that. Is that supposed to happen? Should I try to delete that commit?

Kind regards,

Alexander