optimise drawj.js
small tidy up of effects.js
fixed stroke problem with draw.js
added extend() helper and used it from game_loop.js
added mouse click to input manager for fire
refactor of Input
logic optimisatin for hit detectin loop in app.js, once loop instead of two
fixed shooting enemies not scoring
a pretty serious re-write of game_loop.js to decouple update() and draw() calls along with a re-write of frame_graph.js to reflect this