refactored code in mo_poly.f90 to mo_poly.fypp and replaced mo_poly.f90
added new routines orientpoly (calculate orientation of coords in polygon), mod_pole (modify coords of grid to include poles on Cartesian coord system) and mod_shift (shift longitude values by 180 degrees)
added test cases for new routines and refactored older ones
fixed a small bug in the tests/CMakeLists.txt file that ignored the *.fypp based files