Use file-loader and url-loader

[jussikinnula]

Current WebPack uses copy plugin to copy src/images to target/assets/images. Instead of this we should use file-loader and url-loader to require the assets directly.

Please see details from my other project:
https://github.com/jussikinnula/react-starter/blob/typescript/config/webpack.common.ts#L72-L87

On Stylus -files, files are required by relative path like:
background-image url('./foo.jpg')

On Pug -files, files are required with a require() like:
img([src]="./require('./bar.jpg')")

On TypeScript -files require() is used as well, however, the current implementation of Angular.fi site doesn't have any logic to load images done on TypeScript files side.

[jussikinnula]

Actually on app.component.ts we should require manually all versions of logos (and use relative reference to logos everywhere, pointing towards src/app/logo_xxxx.png), so that the logo versions can be kept visible if someone wants to use them in slides etc. The logos are logo.png, logo.svg, logo-inverse.png and logo-inverse.svg.

[jussikinnula]

After the implementation is finished, also the remaining src/images can be removed, as well as WebPack copy plug-in.