JuK: Check and Update Copyright Headers and Collect any missing information
completed by: Eric Newberry
mentors: Shubham Chaudhary
Update JuK's license headers by adding more information. It's useful to know who contributed to various parts and during which period for statistical reasons. If we get a complete list and manage to maintain it, any future license changes (ex. to GPLv3) will be easier. If there is a incorrect license stated in a header, the copyright holders should be contacted before making the fix.