Merge branch 'configure_help' into develop (PR #212)

Merge branch 'configure_help' into develop (PR #212)

This merge adds -h/--help options to the configure script to print a summary of
the available configure options. The message reads as follows:

  Usage: configure [options]

  where options may be any of the following:

   --nowrf             Disables checks to find the path to the compiled WRF model.
                       This enables some WPS programs to be compiled without
                       requiring WRF to have been compiled, but it will preclude
                       the compilation of WPS programs that depend on the WRF I/O
                       API (geogrid, metgrid, and int2nc).

   --build-grib2-libs  Compiles zlib, libpng, and JasPer libraries from source in
                       the external/ directory, and installs the libraries in
                       grib2/.

   -h/--help           Print this help message and quit.

* configure_help:
  Add -h/--help options to the 'configure' script