Prune github repo

[SarangaR]

The github repo size is currently much too large.

[amillh]

Something like this https://rtyley.github.io/bfg-repo-cleaner/ should work, would just require everyone force pulling/making clean clones of the repo

[ugackMiner53]

There really is no solution that wouldn't require most people to re-clone. If the dirty git history is cloned, no matter what method is used to prune the remote, there's always the chance that they commit it back later.

I haven't personally used BFG repo cleaner, but it's likely much better than the alternatives, like manually scrubbing through and editing the git history with other tools.

(Edit: There's also a lot of branches currently sitting around on the remote. Maybe some of these could be removed? A majority of them seem very out of date.)

[SarangaR]

I'm linking a PR to this where a bunch of dead/unused code has been removed. This will probably not solve any of the git history problems but it at least makes compiling faster.