added commentaries in DString*:__init__ about the three attributes iso639_3_name, transliteration_method, options
SuccessiveTransformations.apply : new argument 'limit_to_the_number_of_transformations'
modified dchars.py to take in account the strange behaviour of the  configparser module which needs to open (on Windows systems) the file utf-8 files with a call to codecs.open .