They would be silently ignored otherwise

Extend the implementation of csr_matrix and csc_matrix in numba. Use those implementations in SparseFromDense

Make sure we don't issue unexpected warnings

Numba sparse: handle dot product between matrices more granularly to reduce the number of of format conversions

* Add comment regarding meaning of '*' operator with sparse matrices

* Implement sparse dot product in numba

* Overload T attribute in numba sparse matrices

* Implement toarray

* Add tocsr

Co-authored-by: Jesse Grabowski <48652735+jessegrabowski@users.noreply.github.com>