Tidy of components

- Moved all components into a single directory like nextjs
 - Made component names consistent with each other
 - Made component names consistent with their export class names
 - Added storybook for a few components with the aim to extend this further.

src/components/Collapser.jsx

@@ -0,0 +1,20 @@
+import React from 'react'
+import PropTypes from 'prop-types'
+import {MdArrowDropDown, MdArrowDropUp} from 'react-icons/md'
+
+export default class Collapser extends React.Component {
+  static propTypes = {
+    isCollapsed: PropTypes.bool.isRequired,
+    style: PropTypes.object,
+  }
+
+  render() {
+    const iconStyle = {
+      width: 20,
+      height: 20,
+      ...this.props.style,
+    }
+    return this.props.isCollapsed ? <MdArrowDropUp style={iconStyle}/> : <MdArrowDropDown style={iconStyle} />
+  }
+}
+