Better navigation with keyboard and mouse

[wischi-chr]

Additional to #4 navigation could be further improved by using settings most people already know from playing (ego-perspective) games.

Key / Mouse	Action
W	move forward (into the screen)
S	move backward
A	side step left
D	side step right
Arrow Up	Look Up
Arrow Down	Look Down
Arrow Left	Look Left
Arrow Right	Look Right
Mouse Move	same as arrow keys (look around)
Shift	Move faster
Ctrl	Move slower