Geometry_oM: Consider removing IGeometry interface from Face and CellRelation

#### Broken rules:

Classes are not true geometrical concepts, but rather topological. Reason for removal show up in cases where you might want to query something out of an abstract geometrical object, such as the BoundingBox. This simply does not make sense for these types of objects in isolation.

#### Suggestions to restore compliance:

Consider removing the IGometry interface by these types of obejcts.