Add recipe diagnostics page

[jayaddison]

Describe the reason for these changes and the problem that they solve

In #94 we describe the basis of a 'recipe debug page' -- an informational display that can surface potential data quality issues by doing two things:

• Displaying the state of the recipe as it is currently stored in the search engine
• Displaying the state of the recipe as it would appear if re-crawled

This change introduces the recipe diagnostics page, which displays both of these in a visual diff.

Recipe content is retrieved as JSON from the diagnostics service, and a diff is performed between the currently-indexed and immediately-crawled versions.

This diff -- and the visual summary -- are generated courtesy of the jsondiffpatch library.

To access the diagnostics information for a recipe, navigate to the recipe detail page for that recipe, and then triple-click on the recipe's title text.

Briefly summarize the changes

1. Add an isolated diagnostics page to the web application
2. Allow recipe title triple-clicks to open the corresponding recipe diagnostics view

How have the changes been tested?

1. Local development testing

List any issues that this change relates to Resolves #94

[jayaddison]

@queencitra No rush, but your feedback would be very welcome on this feature when you have time. It has changed a bit since the original description in #94 - it's a completely separate page, rather than a 'data' tab, and it's accessible by clicking three times on a recipe's title.

Hopefully this should help to view the contents of the data about each recipe, and also to verify any potential fixes.

[jayaddison]

(merging and deploying this current version - feedback is still welcome at any point, this is an iterative development process!)