Finished YANG parser.

    - A RAW commit! This commit contains a known bug - memory
      corruption. This will be fixed in future commits
    - Fixed numerous other problems with memory leaks,
      segmentation faults, made the code more robust
    - Finished parsing YANG files (augment support still to come)
    - Added new testing files, testing file 3 for YANG
      demonstrates the presence of memory corruption bug