Update and rename ScratchPad.md to LESSONPLAN.MD

- Removed the confusing Letter-Number classification system. 
- Suite will now include Lessons and not just exercises.
- Lessons and Assignments will be sequential. L01 => A01 => L02 => A02 and so on...
- Proposed assignments/lessons yet to be completed should be labeled `A00P` until a proper number can be ascertained.