[Prac 16] Added lillian's practical 16 code (linked lists)
[Prac 16] Implemented LinkedSetDouble
[Prac 16] Moved set stuff to its own package
[Prac 16] Added Shape and Rectangle classes
[Prac 16] Added some shape implementations
[Prac 16] Added a canvas for drawing multiple objects onto
[Prac 16] Added and implemented GeometricCalculus
[Prac 16] Implemented final AsciiCanvas with the Drawable interface
[Prac 16] Added extra javadoc comments for properties