taxonomy_csv 6.x-5.1

By Daniel Berthereau: Fixed error of commit to cvs and linked bugs.
By Daniel Berthereau: Merged all taxonomy-csv 6.x branches except 6.x-1.
By Daniel Berthereau: Doxygened some help.

By Daniel Berthereau: Changed cvs HEAD from 6.x to 7.x release.
By Daniel Berthereau: Merged all taxonomy-csv 7.x branches except 7.x-1.
By Daniel Berthereau: Modularized and simplified code and reintegrated line api.
By Daniel Berthereau: Use of new features of Drupal 7 (UI and Field).
By Daniel Berthereau: Implemented synonyms and related terms in 7.x release.
By Daniel Berthereau: Cleaned structure of user interface.
By Daniel Berthereau: Improved speed of tree and polyhierarchical import.
By Daniel Berthereau: Implemented quick import mode: no check of existing terms.
By Daniel Berthereau: Set hierarchy check disabled by default in user interface.
By Daniel Berthereau: Removed special permissions and use 'administer taxonomy'.
By Daniel Berthereau: Removed internal cache and use only core taxonomy ones.
By Daniel Berthereau: Removed utf8 conversion.
#872366 by vipzhicheng: Better support of non-Ascii characters.
#843526 by iAugur: Fixed field name prefix.
#686328 by Alexander N: Fixed double display of PathAuto warning.