cleanup some unused files

[Alizter]

In this PR we cleanup some unused files. Many of these stem from historic build processes which are no longer relevant.

[jdchristensen]

Thanks, it good to get rid of out-of-date stuff. We have a lot of it...

Here are a few things I noticed that look that might be unused or need updating.

References to doctoc:

etc/ci/install_doctoc.sh
sudo -E npm install -g doctoc || exit $?

etc/ci/before_script.sh
    ./install_doctoc.sh || exit $?

STYLE.md
<!-- START doctoc generated TOC please keep comment here to allow auto update -->
<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
<!-- *generated with [DocToc](https://github.com/thlorenz/doctoc)* -->
<!-- END doctoc generated TOC please keep comment here to allow auto update -->

Other things in etc/ci/before_script.sh might be out of date too.

This should be removed:

Makefile.coq.local
#       $(SHOW)'HOQTHMDEP HoTT'

[Alizter]

@jdchristensen From what I can tell, none of the scripts in etc/ci are being used. They are from the Travis CI days. I've removed all of them. I've also done the other suggestions you had.

[jdchristensen]

Were the whitespace changes to STYLE.md intentional? I doubt they affect the output, but we try to avoid unrelated whitespace changes.

Other than that, this LGTM. It's still a draft, so I'm not sure if you have more planned.

[Alizter]

They were not intentional, I will fix them.