Suggestion: move mathematicalShapes schemas from SANDS to Core

[lauramble]

Schemas for mathematical shapes can be useful in contexts unrelated to spatial anchoring in the brain. For example, in microscopy, it can be used to model a field of view (as in the spatial extent of an imaged region).

Therefore, we suggest moving the existing shape schemas (Circle, Ellipse, Rectangle) from openMINDS_SANDS/schemas/mathematicalShapes to openMINDS_core/schemas/miscellaneous, either in a dedicated mathematicalShapes folder or directly in miscellaneous.

[Raphael-Gazzotti]

It is at the moment a soft dependency (not a requirement), so it is not essential to move it yet.
We may reevaluate it when a true dependency is created.

Note from the team: TBD // reevaluated when the microscopy schema will be under PR.