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