KokkosBlas: Add GEMV that wraps BLAS (and cuBLAS)

[kokkos]

KokkosBlas: Add GEMV that wraps BLAS (and cuBLAS)

[crtrott]

OK we need to fix this with respect to BLAS and CuBLAS. The seconds thing is another issue.

[crtrott]

So what does this need to do for Stokhos?

[mhoemmen]

@crtrott When you say "the second thing," do you mean the issue of whether impl_scalar_type == dot_type? That's something specific to Tpetra; I wouldn't expect kokkos-kernels to have to deal with that. Tpetra would prefer to defer to kokkos-kernels in the common case where impl_scalar_type == dot_type, though. Thanks!

So what does this need to do for Stokhos?

For some Stokhos Scalar types in Tpetra, impl_scalar_type != dot_type. Stokhos uses double (or whatever the underlying scalar type is) as the dot_type, since it is the result of the dot product of two Stokhos Scalar types.