Pipe unification and type switching

Created by: ComicIronic

Tanks are now unaries, not pipes. Portable connectors are now unaries, not their own type. Valves are now binaries, T-Valves are now trinaries. Pipes as much as possible now use the general attackby code. Slight changes to pooling code. Removed loads of duplicate code that existed for no real reason. T-Valves now come in manual and digital and mirrored under those types, not the other way around. Mirrored connecting sprites for T-Valves should show up properly now.

Never again.