CMS visual builder (config.yml generator)

**- Do you want to request a *feature* or report a *bug*?**
Feature: a *visual CMS builder* that generates your config.yml to speed up development process and make it easier for newcomers to use NetlifyCMS.

**- What is the current behavior?**
We have to write 50k+ mostly repetitive characters of config.yml and lose our heads when changes need to be made. Validation is also non-satisfactory and almost led me to abandon the CMS at first - and this is a thing the CMS generator could easily help.

**- The plan**
The idea is building a standalone generator at first, test it and make it work for most use cases, then, eventually, integrate it into the docs for beginners to use.

I've already started the project in **[this repo](https://github.com/hcavalieri/netlifycms-generator)** and laid out the foundations for it. The code is far from optimized/good and you might get lost in it a little bit, but I believe the architecture and planned features are on the right track.

You can **take a look at it** and its basic functionalities **[here](https://cms-generator.netlify.com/)**, although you won't be able to do anything special here. Any specific discussion about the generator should happen inside the current repo to avoid flooding this topic :)

**- You can help!**
In order to get this ready before the end of April (I won't be able to put in many hours this month 😢), we need your help, be it with testing for bugs, auditing the code or writing new functionalities! This project can be a huge step up for NetlifyCMS as we'll be able to reach even those who are crude with the JAMstack, grow its popularity and, therefore, make it more solid. **Let's do it!** 😄