Refactor Icon component to use Sprite

[iegik]

Implements #63

This makes ability to add Icons by their use:link in the SVG sprite

Usage:

// Sprite.tsx

// eslint-disable-next-line import/no-webpack-loader-syntax
import HomeIcon from '!!raw-loader!icons/home.svg';
// eslint-disable-next-line import/no-webpack-loader-syntax
import DefaultAvatar from '!!raw-loader!icons/DefaultAvatar.svg';
// eslint-disable-next-line import/no-webpack-loader-syntax
import PlusIcon from '!!raw-loader!icons/plus.svg';

const icons = {
  'home': HomeIcon,
  'DefaultAvatar': DefaultAvatar,
  'plus': PlusIcon,
};

      /* somewhere in the app's page */
      <Icon name="home" />

      /* somewhere on App.tsx */
      <Sprite />