Introduce MatrixFree Operator factory and use it for device
This makes it impossible for the 'device' code to fall back to host-code for matrix-based solvers, so remove matrix-based unit test
Closes: #71 (closed)
This makes it impossible for the 'device' code to fall back to host-code for matrix-based solvers, so remove matrix-based unit test
Closes: #71 (closed)