Check if output and restart file path is writeable

[scrasmussen]

TYPE: new feature

KEYWORDS: IO Files, Namelist Validation

SOURCE: Soren Rasmussen, NCAR

DESCRIPTION OF CHANGES: New subroutine checks if output and restart file paths are writeable. When the namelist is read, the existence of the directories where the output and restart files are being written to is checked. If they do not exist the routine will report error then, rather than throwing an error later when the NetCDF library tries to write to the file.

TESTS CONDUCTED: Checked that the subroutine functioned correctly for the following input file strings

output_file = "output/foo/icar_out_"
output_file = "output/icar_out_"
output_file = "output//icar_out_"
output_file = "./icar_out_"
output_file = "icar_out_"

Checklist

• Closes issue #xxxx (An issue must exist or be created to be closed. The
  issue describes and documents the problem and general solution, the PR
  describes the technical details of the solution.)
• Tests added (unit tests and/or regression/integration tests)
• Backwards compatible
• Requires new files? If so, how to generate them.
• Fully documented

[gutmann]

Thanks, looks like quite a straightforward addition that could save a lot of pain!