Store more operator arrays

[JaredCrean2]

With the various experiments we are doing, it would be helpful to have more of the operator matrices stored as part of the SBP type, particularly D, S, R (in addition to R.'), and maybe E.

@Hicken if its ok with you, I can implement this because everything can be derived from Q and R.

[JaredCrean2]

Also, storing the inverse permutation vectors would be useful (for applying P.')

[jehicken]

For numerical experiments, we can construct these operators as we need them. For example, I am not opposed to having helper functions that use the sbp types to construct these matrices; however, the only matrix I see value in storing, in addition to the ones already stored, is S.

Can you provide a compelling argument why any of the other operators should be stored?