This introduces functionality for creating strategies for matrices and
vectors, as well as an implementation of Arbitrary.
Strategies for the geometric types (Point3, Quaternion etc.) are not
currently part of this contribution.
The current strategy implementation for matrices has some limitations
that lead to suboptimal shrinking behavior. This is documented in the
module-level docs, with some additional comments in the code.
Sébastien Crozet
Rémi Lauzier
Violeta Hernández
Andreas Longva