Initialization using SpatialOps::Grid is problematic

Zodiac uses SVolField variables as its field type. It is currently using SpatialOps::Grid to initialize the parametric variables over which the simulation is run.

There are a few problems with this:

• SVolField is a cell-centered variable, meaning that if we specify n points over [min,max], we won't get a point at min and max - rather, they will be offset by half of the spacing.
• We may want to have log-spaced fields, or fields at specified values, etc. These will require initialization other than using SpatialOps::Grid

A possible solution that would allow us to leverage SpatialOps::Grid is to define a Vertex field type in SpatialOps that lives on vertices rather than volumes or faces.