Update member function in isoSurface.C to support dynamic meshes

[ancolli]

Modified the member function to be compatible with changing meshes.
The implementation follows the approach used in isoAlpha.C, which has been verified to work correctly with mesh motion.

[HenningScheufler]

thanks for the PR can you merge into of2406?

[ancolli]

Done!

[isoAdvector]

Looking good!

facePts seems to be unused - if so, remove. Same in isoAlpha.

By the way: Difference between isoAlpha and isoSurface needs documentation.
Current descritption in header of isoSurface.H: "Water saturation curve by Roche-Magnus"
Replace with proper description (main diff from isoAlpha: Support for LTS and dVf_ replaced by alphaPhi, if I remember correctly).

Should isoAlpha and isoSurface eventually be merged?

[ancolli]

Hi, isoSurface is the only one working in my case. I did not go into the details of the differences between the two methods yet. Regarding the underlying theory, should I refer to:
Oenby J, Bredmose H, Jasak H. 2016. A computational method for sharp interface advection. R. Soc. Open Sci. 3: 160405.
http://dx.doi.org/10.1098/rsos.160405?