Makes register download / API options more prominent

[injms]

Context

Getting access to a Register's data means a user needs to choose whether they want to download the data or use the API. This choice was the second step in the flow - but surfacing the choice sooner highlights the different methods offered and removes a step in the process.

The card has the prototype and the content documents attached to it.

Changes proposed in this pull request

• Removes the 'Choose access' step
• Adds API and download options onto register page
• Removes custom form header styles
• Replaces old highlight boxes styles with new
• Small amount of refactoring, removing old Elements and adding new Design System
• Rewrote tests to take into account new flow

Guidance to review

• Look out for anything else that could be removed
• Layout uses display: flex, so falls back to floats for Internet Explorer 8 to 10

[gidsg]

LGTM (aside from minor comment) 👍 🍎