[doc] cleanup all unwanted code

.gitignore

.gitlab-ci.yml

conda/meta.yaml

conda/yum_requirements.txt

doc/_static/copybutton.js

doc/_templates/config.rst

doc/conf.py

doc/envs/v262py27.yaml

doc/envs/v262py35.yaml

doc/envs/v270py27.yaml

doc/envs/v270py35.yaml

doc/envs/v300py27.yaml

doc/envs/v300py36.yaml

doc/help.rst

doc/img/favicon.ico

doc/img/logo.png

doc/index.rst

doc/install.rst

doc/links.rst

doc/packages.rst