Fix detection of fuzzy strings in gettext files
Display "(fuzzy)" after line number and colon in error messages
Use argparse module to parse command line arguments

Long name for arguments are now allowed.
Arguments have been renamed: '-n' to '-l', '-s' to '-w'.
Add option "-s" (or "--spelling") to check spelling and option "--pwl" to use a personal word list

The spelling is checked with module "python-enchant".
Add option "--extract" to extract translations
Add check of spelling in README.md