Inheritable, overridable class and instance data accessor creation

 Class::Data::Accessor is the marriage of Class::Accessor and
 Class::Data::Inheritable into a single module. It is used for creating
 accessors to class properties that is overridable in subclasses as well as in
 class instances.
 .
 For example:
 .
   Pere::Ubu->mk_classaccessor('Suitcase');
 .
 will generate the method Suitcase() in the class Pere::Ubu.
 .
 This new method can be used to get and set a piece of class property.
 .
   Pere::Ubu->Suitcase('Red');
   $suitcase = Pere::Ubu->Suitcase;