Change order of parameters to put World last

World parameter moved to the end of the parameters so that it is
possible to build pipelines of World -> World functions. Tidied up
comments.
Added Markers and changed order of parameters

Change order of parameters to put World as last parameters to make the
world transforming functions of type World -> World. Added code for
Markers. Remove commented out code. Include comments from puzzles file.
Add solution for Engine
Improved comment, layout and type declarations

Moved (>>>) reverse composition to end of the line to improve
readability. Added comments. Added missing type declarations
Renamed files to removed numbers from file-names

Previously the files were ordered with file names at the beginning to
show the order they should be tackled. Numbers have been removed so that
the file names match the module names.
Update Graphics

Add solution for Graphics and tweak puzzle file to keep in line
Merge pull request #8 from derekwright/master

Add Graphics, update World and Engine