Fix sass coding style and modification date on main.css.

.sass-lint.yml

gulpfile.js

opentech/static_src/src/sass/apply/abstracts/_functions.scss

opentech/static_src/src/sass/apply/abstracts/_mixins.scss

opentech/static_src/src/sass/apply/abstracts/_variables.scss

.../static_src/src/sass/apply/components/_activity-feed.scss

opentech/static_src/src/sass/apply/components/_button.scss

opentech/static_src/src/sass/apply/components/_feed.scss

opentech/static_src/src/sass/apply/components/_form.scss

opentech/static_src/src/sass/apply/components/_heading.scss

opentech/static_src/src/sass/apply/components/_icon.scss

opentech/static_src/src/sass/apply/components/_link.scss

opentech/static_src/src/sass/apply/components/_nav.scss

...tech/static_src/src/sass/apply/components/_rich-text.scss

opentech/static_src/src/sass/apply/components/_select2.scss

opentech/static_src/src/sass/apply/components/_table.scss

opentech/static_src/src/sass/apply/components/_tabs.scss

opentech/static_src/src/sass/apply/components/_wrapper.scss

opentech/static_src/src/sass/apply/fancybox.scss

opentech/static_src/src/sass/apply/layout/_header.scss