Minor tweaks

I've scaled all input data down by 4 to make it easier to develop on
this machine with an integrated card, and made a few small tweaks to
make it easier to view/navigate
Switch to using indexed triangles for landscape
Compute the normal for each terrain vertex

Terrain shader temporarily disables as it doesn't support lighting yet
Convert Camera and Landscape to use glm for vector operations
Implement basic lighting for terrain shader