Fix problem with duplicated class id and wrong tax class definition
Merge branch 'development' of git://github.com/firegento/firegento-magesetup into development

# By Andreas von Studnitz
# Via Andreas von Studnitz
* 'development' of git://github.com/firegento/firegento-magesetup:
  [+FEATURE] Copy "is_initialized" flag from GermanSetup to MageSetup for Upgrades (#12)
  [~TASK] Update english translation file to reflect latest changes
  [+TASK] Update feature and overview texts with new feature (customer tax class assignment)
  [+FEATURE] Update tax classes of existing customer groups, provide a section in the setup form this (fixes #9)