set enemy helicopter to not paint if outside of visibile range of player
added some documentation to main, eliminated a magic number
Added -1 duration animation capability to further remove character
classes from implementation of display. Passing visual information
should ONLY be through animations after this update.
updated task list, improved some documentation and deprecated some
unused functions
moved background, made it animation, removed background refs in
playercharacter, added a bit more documentation, made background move
with player again.
standardized use of Position in classes and added constructors to it and
the NonPlayerCharacter classes to support standardized use.