The first wails of enemies

Enemies start talking! Some growl when they sense you're close, some continuously utter ominous noises, some do even worse... and more is to come ;) Also, the first proper HUD makes its debut (although it is going to change)!

CHANGELOG

• Extended sound system.
• Started adding enemies sounds.
• Centered entrance area.
• Added HUD.
• Touched up / adapted tiles graphics.
• Added some information to the manual.
• Made many internal improvements/additions/bugfixes.