version 0.0.0.9013 2017-03-16
  * new object class 'coverconvet'
  * methods for 'coverconvert'
  * function 'transform' to convert cover codes into percentage

version 0.0.0.9014 2017-03-19
  * new validation rule: duplicated combinations 'name + author' are not allowed
  * data 'Easplist' modified to fulfil the last rule
  * new method 'as.list'
