Data Driven Configuration Comment Box on each Level

[JohnZeman]

Right now each data-driven category properties has a description section where we can leave a description for ourselves as to what that DD category does.  I would find it very useful if we also had a per level description box where we could leave a note for ourselves while configuring each level of a DD category (because sometimes I'll later go back and wonder why I configured a particular level to do what it does).

For example I might write something like "This level extracts the month name in long format."