Added webpack.ProvidePlugin for most used imports

Removed imports of React, connect, PropTypes throughout
Removed the "React" in React.Component/PureComponent

app/javascript/gabsocial/features/ui/components/column_link.js

@@ -1,5 +1,3 @@
-import React from 'react';
-import PropTypes from 'prop-types';
 import { Link } from 'react-router-dom';
 import Icon from 'gabsocial/components/icon';