P_N Closure

(Reopening mergerequest !10 (merged), that was somehow closed)

This merge request contains all work done with respect to the implementation of

• P_N Solver

• P_N Unit Tests

• Adapted Fluxes

• Code Restructuring: Indroduced new folders, tidied up #include statements

• Spherical harmonics basis + unit tests

• untested version of MN Solver

• Changed CFL number computation. How to use P_N Solver:

• Select as option SOLVER=PN_SOLVER

• Option MAX_ORDER_SOLVER is the order N of the PN equations

• One can tune the flux matrices with the Option CLEAN_FLUX_MATRICES = YES. This will set very low floating point values to zero in the (sparse) FLux matrices. This should improve floating point arithmetic stability.

Corresponding issues: #42 (closed), #30 (closed), #41 (closed), #39 (closed) , #38 (closed)