Add procedure `get_slice_dir`

Common/get_slice_dir.f90

+module get_slice_dir_m
+
+  implicit none
+
+contains
+
+  pure function get_slice_dir(shpc_dir, cyclone, slice)
+
+    character(len = :), allocatable:: get_slice_dir
+    character(len = *), intent(in):: shpc_dir
+    logical, intent(in):: cyclone
+    integer, intent(in):: slice
+
+    ! Local:
+    character(len = 10) slice_part
+
+    !-------------------------------------------------------------
+
+    write(unit = slice_part, fmt = "(a, i0)") "Slice_", slice
+
+    if (cyclone) then
+       get_slice_dir = shpc_dir // "/Cyclones/" // trim(slice_part)
+    else
+       get_slice_dir = shpc_dir // "/Anticyclones/" // trim(slice_part)
+    end if
+
+  end function get_slice_dir
+
+end module get_slice_dir_m