[Geometry] Added sizes() method to BBox class
[Geometry] Added center() method to BBox class.
[Geometry] Modified header deps in `Conic.hpp`
[Geometry] Moved impl. of projective transform

Moved implementation of projective transforms from `Conic.hpp` to
`MatrixBasedObject.hpp`. Be careful: the implementation is not yet
usable.
[Geometry] replaced `convexSectorArea` by `sectorArea` in `Ellipse` class.
[Geometry] Removed `wellDefined` method in `Ellipse` class.
[Geometry] Added documentation to `inside` function for `Ellipse`.
[Geometry] Added rotated BBox function for `Ellipse` class
[Geometry][WIP] Investigating numerical accuracy issue in ellipse intersections.

Some intersection problem instances are very badly-conditioned. So need
to solve ASAP.
[Geometry][WIP] Disabled previous unit tests to focus on ellipse intersections.