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/compose/containers/upload_container.js

@@ -1,4 +1,3 @@
-import { connect } from 'react-redux';
 import Upload from '../components/upload';
 import { undoUploadCompose, changeUploadCompose } from '../../../actions/compose';
 import { openModal } from '../../../actions/modal';