Tolerances in the BDF solver in KokkosKernels.

[odiazib]

Newton and time advancement parameters in the BDF solver of Kokkos Kernels are hard-coded. We must coordinate with the KokkosKernels team to move these parameters as inputs.

• Newton solver parameters are hard-coded here.

• Both atol and rtol are employed in the Newton solver and in the computation of the initial time step.

• max_step (I believe this is the maximum time step) is computed as: max_step = (t_end - t_start) / 10;