Improve the Design System to improve stability and usability for future development and maintenance

[mariongalley]

* It's clear how the world will be different when the work is completed

The Design System will be restructured so that there is a clear delineation between core components and project components. This will allow us to retain a higher degree of stability in the core components and prevent unexpected interface changes across different services.

* It's clear what will and won't be done

We will restructure the existing components tree so that we can more clearly identify where a component is being used and the implications of updates.

We should increase in the number of prototype pages so that we have a better idea of the impact across different parts of each project and retain an understanding of how those pages should look.

We could include visual diff tools (such as backstop.js). This would require a test suite, possible dev/test/live deploys and the ability to deploy or inject new branches. There is a fairly high degree of time investment and complexity in this.

* Any uncertainty, assumptions, dependencies or constraints are recorded

* There's an order-of-magnitude estimate of how long it will take

Days - weeks

* The work's been approved by someone at 360

* There's links to everything that's written down about the work - such as plan.io tickets, GitHub issues

https://github.com/ThreeSixtyGiving/360-ds

[mariongalley]

Improve the Design System to improve stability and usability for future development and maintenance