Pipe rendering rewrite

- Complete rewrite of pipe rendering code. It now selects icons from a shared cache.
- Manifolds and other devices (pumps, filters, etc.) now match the color of the connected pipes.
- Updated omni devices to use the shared cache.
- Set separate pipe color definitions.
- Cleaned up a lot of pipe code, converting it to absolute paths and removing old commented out code.
- Tweaked t-ray rendering code.
- Tweaked pipe painter.
- Enhanced pipe checking debug command.
- Expanded tank capacity and resprited them.
Atmos update tweaks

- Updated pump and volume pump icons
- Reverted air scrubber icon
- Fixed passive gate icon
- Updated pipe_item sprites
- Fixed an oversight in the pipe color check
- Cleaned up the map
Pipe cleanup

- Tidied up a couple of remaining pipes
- Removed overlapping pipes
- Removed step_x, step_y vars