Add basic Bootstrap theme to Studio

cms/envs/common.py

cms/static/sass/_build-v1.scss

cms/static/sass/_build-v2.scss

cms/static/sass/bootstrap/_base.scss

cms/static/sass/bootstrap/_components.scss

cms/static/sass/bootstrap/_footer.scss

cms/static/sass/bootstrap/_header.scss

cms/static/sass/bootstrap/_layouts.scss

cms/static/sass/bootstrap/_mixins.scss

cms/static/sass/bootstrap/_navigation.scss

cms/static/sass/bootstrap/_variables.scss

cms/static/sass/bootstrap/studio-main.scss

cms/static/sass/partials/bootstrap/_theme.scss

cms/static/sass/partials/cms/base/_variables.scss

cms/templates/base.html

cms/templates/ux/reference/_note-usage.html

cms/templates/ux/reference/bootstrap/test.html

cms/templates/ux/reference/index.html

cms/templates/ux/reference/pattern-library/test.html

lms/templates/ux/reference/index.html