Slight refactoring in the indexer code
* Moved safe_unicode.py to parser_utils.py
* Started move of several pieces of shared code to parser utils
* Started move of several constants into a separate constants file
* Replaced several print functions with info/warn/debug/err wrapper
  functions
* Removed several unused cli params from indexer
* Several fixes in MetadataParser to work with the newer backends
* Reworked hachoir parser to the new data structure