Create unit tests for comparing metadata headers against Fortran

[gold2718]

capgen needs to compare a metadata header against the associated CCPP Fortran interface routine.

• Create unit tests that do the following:
  • Read a metadata file (to collect the metadata headers)
  • Read the associated CCPP Fortran scheme file (to collect Fortran interfaces)
  • Compare the metadata header against the Fortran
• Tests should include
  • Correctly identify when the metadata file matches the Fortran, even if the routines are not in the same order
  • Correctly detect a missing metadata header
  • Correctly detect a missing Fortran interface
  • Correctly detect a mismatch between the metadata and the Fortran

This set of tests is testing the parse_scheme_files and parse_host_model_files functions in ccpp_capgen.py which perform the operations in the first bullet above. Each test should call one of these functions.