Print Preview is now generated in the background and displays a spinner while it is generating.

Halved time to load the code grading view.
Fixed file directory search duplicating.
No longer 'misses' some .java files, then say that we have .java files.
Fixed simple unit tests when they wouldn't compile.
Test description overlay no longer auto-closes when errors occur testing.
Fixed stackoverflow with printing
Fixed running simple unit tests multiple times if multiple methods applied.