Mailroom Madness w/ Dicts, Copy Src 2 Dest, and Print Path of Files

Updates to Mailroom Madness:
- Using dicts where possible, including main menu
- Writes all un-written letters to every donor
- Tracks which letters have been created

Since they were included in the same assignment on Canvas, Copy Source to Destination & Print Path of Files are also included in this branch and pull request