Merge pull request #128 from terrence2/sky

This is now the core of nitrogen.

Merge pull request #127 from terrence2/port-to-catalog

Convert everything else to catalog.

Merge pull request #126 from terrence2/bitrot

Start cauterizing some bit rot

Merge pull request #125 from terrence2/evict-non-fa-code

Evict more code that is generic to all flight simulators

Merge pull request #124 from terrence2/shader_globals

Port to nitrogen's shader global data.

Merge pull request #123 from terrence2/generic-fnt

Make glyph drawing abstract over the font

Merge pull request #122 from terrence2/library

Refactor Library as a pluggable component

Merge pull request #121 from terrence2/port_to_nitrogen

Port to nitrogen

Start porting base layer.

Merge pull request #120 from terrence2/tile-index-8Jul20

Pave the way for tiles