Adapted meshSearch and sampledTriSurfaceMesh to use it.

- remove all corresponding logic from foamExec

Conflicts:
	bin/foamExec

- This lets foamExec use foamEtcFile as well, but debian packaging
  still needs some work

Include revert for ca7a6f51 + aec1bace
- Henry's version is simpler.

PV3FoamReader: Use the vol-field name rather than volPointInterpolate<vol-field name> for the VTK point fields

- avoids things like "volPointInterpolate(U)", but will likely cause
  issues when used together with identically named Lagrangian fields!