It turns out the line `let Punishments = module.exports;` makes it into
`any`, and disables nearly all typechecking of anything to do with
`Punishments`. This refactor fixes that, and also fixes a bunch of flaws
newly caught by TypeScript.
I tried my best not to make any changes to actual functionality. These
changes should be effectively purely code cleanup.
Also move mods/ to data/mods/
This makes PS more monorepo-like. The intent is to further separate
the sim and the server code, but without fully committing to splitting
the repository itself.
We now support `./pokemon-showdown start` in addition to
`./pokemon-showdown`. I'm not clear which I want to be the default
yet.