Major CSS revamp

- Get rid of Bootstrap (except we still rely on some JS)
- Use BEM class names
- Rework variables/theme config
- Fix various bugs, including some on mobile

The CSS is still not ideal – it needs to be cleaned up some more. But
that can be a focus for after beta.

js/forum/src/components/AvatarEditor.js

@@ -37,15 +37,14 @@ export default class AvatarEditor extends Component {
     const user = this.props.user;
 
     return (
-      <div className={'avatar-editor dropdown ' + this.props.className + (this.loading ? ' loading' : '')}>
+      <div className={'AvatarEditor Dropdown ' + this.props.className + (this.loading ? ' loading' : '')}>
         {avatar(user)}
-        <a className="dropdown-toggle"
-          href="javascript:;"
+        <a className="Dropdown-toggle"
           data-toggle="dropdown"
           onclick={this.quickUpload.bind(this)}>
-          {this.loading ? LoadingIndicator.component() : icon('pencil', {className: 'icon'})}
+          {this.loading ? LoadingIndicator.component() : icon('pencil')}
         </a>
-        <ul className="dropdown-menu">
+        <ul className="Dropdown-menu Menu">
           {listItems(this.controlItems().toArray())}
         </ul>
       </div>