Polynomial reconstruction in SharpClaw

This PR adds a routine for polynomial based reconstruction in SharpClaw. In detail,

 - 4th and 6th order Polynomial reconstrcution
 - 8th and 10th order reconstruction are also included but have not been fully tested yet
 - renames "weno_order" to "interpolation_order"
 - deallocate calls for WENO5 and Poly_comp
 - sets number of ghost cells for either Weno or Poly in solver
 - documentation

Just a note: renaming `weno_order` to `reconstruction_order` is backward-incompatible, but it is a small enough change that I think it's okay for this to go into 5.3.