[WIP] Boot camps history restore

**Please do not merge this Pull Request yet**

This injects about 6 MB of `boot-camps` history into the `bc` repository, specifically all history for files in the tree at https://github.com/swcarpentry/boot-camps/commit/5b42aeb0492c8d581c77619514fbfbffc2045c19.

I got here by following these steps:

## Cleaning up boot-camps

```
git ls-files > keep-these.txt
git filter-branch --force --index-filter "git rm  --ignore-unmatch --cached -qr . ; cat $PWD/keep-these.txt | gxargs git reset -q \$GIT_COMMIT --" --prune-empty --tag-name-filter cat -- --all
rm -rf .git/refs/original/
git reflog expire --expire=now --all
git gc --prune=now
git gc --aggressive --prune=now
```

## Merging in history with state reset to current state of bc
```
git branch bc-first-commit 328d742231cea360e11469b8a024e20d0686e723
git read-tree --reset bc-first-commit
git commit -m "Sync with bc original state"
git merge bc-first-commit
git clean -xdf
git checkout README.md
git merge --no-ff swcarpentry/gh-pages
```

This PR needs discussion and review before we merge it in.  

We should check that it correctly:

[ ] Restores commit history/provenance of files (commands like `git blame` and `git log --follow -p file` work
[ ] Achieves the right balance of size vs. preserved history
[ ] Doesn't miss anything important

Note: that this does not automatically resolve https://github.com/swcarpentry/bc/issues/41 because the original reproducible_workflow file was stored in an archival branch and never merged to master.  

I'll need to manually go through and merge those files in.  I'm doing everything possible to avoid rebasing, since `bc` is now effectively *in the wild*.  Any help in identifying files without proper provenance in `bc` and their history in `boot-camps`, testing provenance of files that exist, and verifying that tools like `git blame` and `git log --follow -p` work is appreciated.