add tileset, light plugin and first sewer level
add hud and refine sewer level
basher sprite width 320px
add fragcastle sprite preview weltmeister plugin
add sprites for rocket and rocket launcher

part of #55.
Merge branch 'sewers-and-lighting'

Conflicts:
	lib/game/directors/hud.js
	lib/game/entities/player.js
	lib/game/main.js
	media/basher.png