Ops for CalibratedSpace

There is no convenient way to compute statistics using e.g. `Ops.Geometric.Size` for `CalibratedSpace`.

Should Ops that compute stats for calibrated data be added on a per case basis for now? Does it even make sense to approach this issue before the data model has undergone the announced re-structuring?

Start with the issue discussion and the referenced Ops.Geometric.Size and CalibratedSpace concepts; no file, test, or entry point is named. First determine how the announced data-model restructuring affects calibrated-data statistics and whether per-case Ops are still appropriate. Done requires a settled scope and implementation plan for the statistics operations.

Written by the indexing model from the issue text.