REFACTOR - move to nunjucks

[sturobson]

As discussed in person (14/03/19).

We should move the templating engine used for the Visual Framework component library from handlebars to Nunjucks.

Things to do:

• swap out the fractal engine to use Nunjucks (https://github.com/frctl/nunjucks) for components and docks.
• change the handlebars helpers to Nunjucks as needed.
• update the components to use Nunjucks syntax where needed.
• bring in REFACTOR - Make use of the .yml file for pattern data #1 to make use of .yml so we're including components within components.

[sturobson]

@khawkins98 any considerations I've missed here? Feel free to edit.

[khawkins98]

Related to #302

I think we're mostly done here?

[sturobson]

Yep - I've pretty much duplicated #1 as #316