Chore: Implement documentation comments for maintenance purposes.

[bconlon1]

Purposes

• Explanations of what code does.
• Explanations of what mixins do and where they are placed.
• Explanations of math and what it's intended to do.
• Explanations of where code is vanilla copy.
• Make sure all ATs are in usage/are necessary and documented to where they're used.

Details

• Code explanation.
• Class explanations can be put in place of methods for small classes where necessary, like packets.

[bconlon1]

~~Will likely dedicate time to this after the package organization/cleanup.~~

[raptor494]

~~putting this here before i forget: code in AerogelStairsBlock#hidesNeighborFace is based off of code in Block#shouldRenderFace~~