Finished Implementing Library Gui & Fixed a lot of bugs

Fixed junit testing gui NPE
Fixed a instance of not repainting on the swing thread
Fixed crashing with a JUnit Test with a empty path
Fixed crash with library running code.
Libraries are now deleted from dropbox when they are no longer needed.
Fixed crash when junit testing and the unit testing file didn't exist in dropbox anymore.
Fixed watching file when editing JUnit Tests
Added spinner to closing overlay.
Discovered and fixed pretty huge crash bug with all "unlimited add" components.
Fixed junit test files getting renamed when uploading then erroring because they were renamed (now it renames them back locally when testing)
Now downloads libraries upon running code that requires them
Run button is now threaded more
Fixed bug that caused unneccisary junit testing at the start of every session if a junit test was modified after an assignment was submitted.
Fixed unit testing overlay flickering when there were no unit tests to run.
    It now only shows up when a test is run.
Fixed JUnit test files not downloading
Fixed not rerunning unit tests after modifying a JUnit Test File.
Fixed unit tests not respecting libraries to run with.
Fixed not validating email address