Add build pipeline, improve JavaScript

[andreasremdt]

Hey Andi,

I just created this new PR to prevent some merge/rebase chaos with the old one.
This PR contains the following changes:

• Installed gulp-babel and @babel/env. These are used for JavaScript transpilation, meaning that you can use ES6 (like const, let, etc.) while having support for older browsers, such as Safari 9.
• Changed the Gulp pipeline to also transpile the JavaScript.
• Moved the raw, unprocessed Sass and JavaScript files into a new folder src. When Gulp has ran, it will put the processed (and ready-to-use) files into resources/(js|css), like they where before. Meaning that from now on, you should edit the Sass in and JavaScript in the src directory and let Gulp put them into resources.
• Updated simple-translator to version 2.0.2. It now supports more browsers, is already transpiled and could also be loaded from a CDN. The API has also slightly changed.
• In package.json, there were 3 dependencies that had version numbers referenced to some GitHub repos, which prevented a successful installation on my machine. I added the latest version numbers, if you don't want this let me know.
• I installed and used the whatwg-fetch polyfill which should enable Safari to use the simple translator.
• added Prettier to have consistent formatting for both JavaScript & SCSS

[andi34]

@andi34 @andreasremdt I've tested the whatwg-fetch polyfill in simple-translator as provided in above snapshot - works great on iOS 9 / iPad2, thanks a million.

I found one more small thing to be adjusted, in order to make it work with Photobooth on iPad2.

There seems to be an Javascript ES6 TypeError in Safari & IE when iterating over a NodeList object using forEach. Along that comment, I tried the following change in the simple-translatorcode-base, file translate.js, member function translatePageTo:

<                     elements.forEach(function(element) {
---
>                     Array.from(elements).forEach(function(element) {

which then made Photobooth translations work perfectly well on iPad2.

I tried to provide a simple PR but was not able to find the repo / branch where the backward compatible code base resides which is included in the snapshot (i.e. no more use of arrow function). If you are ok to take it from here would be great or let me know where to look and I am happy to provide a PR for this change.

Once more thanks for all the support and your willingness to go beyond, and to make it work.

[andreasremdt]

I just added Prettier to have consistent formatting for both JavaScript & SCSS. If you don't like the formatting (for example the 80 characters max-width which I could understand) let me know, we can still tweak the settings.

[andi34]

I'll fix that later today

[andi34]

rebased on dev branch. will merge once i get feedback :)