ENH: change location of static ensight geometry (#2079)

Historically the "geometry" for static meshes was placed under
directly in the EnSight case directory.

Eg,

     ensight/ensight.case
     ensight/geometry
     ensight/data/000001
     ensight/data/000002 ...

This generally works ok, but relocating it to a constant data directory
Eg
     ensight/ensight.case
     ensight/data/constant/geometry
     ensight/data/000001
     ensight/data/000002 ...

Improves handling and avoids potential collisions when adding in
additional mesh regions