Update Chapter 6 exercises.
Fix greatest common factor exercise.
Add exercises for Java classes
Add exercises for inheritance.
Reorganize chapter 8 and 9 exercises.
Added exercise for Chapter 9, "Advanced classes"
Move basic array exercises to Chapter 4, Loops.
Add/move more exercises.
Hide bin ignore
Rename exercises
Cleanup exercises post last workshop
Cleanup and augment exercises
Fix project name
Cleanup exercises for chapters 4+5
Move the median and mode in chap 6 as a bonus challenge
Fix typo in chap 8 ex 2