Token handler that inserts a counter. Examples:
- [C] - inserts counter, as defined on the dialog
- [C10] - inserts counter starting at 10
- [C10,2] - inserts counter starting at 10, step by 2
- [C10,-2] - inserts counter starting at 10, step by -2
- [C10,2,3] - inserts counter starting at 10, step by 2, use 3 digits to display
- [C10,,3] - inserts counter starting at 10, step by as defined on the dialog, use 3 digits to display
@author Mariusz Jakubowski