Merge branch 'refactor-styles' into 'master'

Refactor css structure

Related to #3025 

cc @skyruler @DouweM @rspeicher @vsizov 

See merge request !1571

app/assets/stylesheets/application.scss

@@ -11,59 +11,41 @@
  *= require cal-heatmap
 */
 
+/*
+ * Welcome to GitLab css!
+ * If you need to add or modify UI component that is common for many pages
+ * like a table or typography then make changes in the framework/ directory.
+ * If you need to add unique style that should affect only one page - use pages/
+ * directory.
+ */
 
-@import "base/fonts";
-@import "base/variables";
-@import "base/mixins";
-@import "base/layout";
-
-
-/**
- * Customized Twitter bootstrap
+/*
+ * GitLab UI framework
  */
-@import 'base/gl_variables';
-@import 'base/gl_bootstrap';
+@import "framework";
 
-/**
+/*
  * NProgress load bar css
  */
 @import 'nprogress';
 @import 'nprogress-bootstrap';
 
-/**
+/*
  * Font icons
- *
  */
 @import "font-awesome";
 
-/**
- * UI themes:
- */
-@import "themes/**/*";
-
-/**
- * Generic css (forms, nav etc):
- */
-@import "generic/**/*";
-
-/**
+/*
  * Page specific styles (issues, projects etc):
  */
-
 @import "pages/**/*";
 
-/**
+/*
  * Code highlight
  */
 @import "highlight/**/*";
 
-/**
+/*
  * Styles for JS behaviors.
  */
 @import "behaviors.scss";
\ No newline at end of file
-
-/**
- * CI specific styles:
- */
-@import "ci/**/*";
-

app/assets/stylesheets/framework.scss

+@import "framework/fonts";
+@import "framework/variables";
+@import "framework/mixins";
+@import "framework/layout";
+@import 'framework/gl_variables';
+@import 'framework/gl_bootstrap';
+@import "framework/avatar.scss";
+@import "framework/blocks.scss";
+@import "framework/buttons.scss";
+@import "framework/calendar.scss";
+@import "framework/callout.scss";
+@import "framework/common.scss";
+@import "framework/files.scss";
+@import "framework/filters.scss";
+@import "framework/flash.scss";
+@import "framework/forms.scss";
+@import "framework/gfm.scss";
+@import "framework/gitlab-theme.scss";
+@import "framework/header.scss";
+@import "framework/highlight.scss";
+@import "framework/issue_box.scss";
+@import "framework/jquery.scss";
+@import "framework/lists.scss";
+@import "framework/markdown_area.scss";
+@import "framework/mobile.scss";
+@import "framework/pagination.scss";
+@import "framework/selects.scss";
+@import "framework/sidebar.scss";
+@import "framework/tables.scss";
+@import "framework/timeline.scss";
+@import "framework/typography.scss";
+@import "framework/zen.scss";