PTypeInfo
PSpecialisedConstructors
PCoercion
PConversion
PDoubleArrayOutput
Go to stable matrix-api 0.0.8.  Add equiv.
PMatrixScaling
PMatrixAdd
PMatrixOps
PSummable
PMathsFunctions
Move blocks of code, no fn change.
PMatrixSubComponents
PFunctionalOperations
All optional matrix-api protocols implemented except for mutability and vectors.