Reorganize Constants.java

[amb2127]

Navigating the Constants file is a hellscape right now, anything could be anywhere and everywhere and it's just very annoying to look through. We should reorganize this in a manner that would be helpful to use to read through again later.

There are a few ways we could go about this:

Grouping related constants into subclasses
Grouping related constants with whitespace
Separate constants into separate files

I think this warrants a discussion.