Addition of five new case studies

[petertait]

This request includes 5 new case studies: Bybox, AZ Overview, AZ CI Portal, PwC and National Express (c2c).

Before merging please triple check the content is a-okay to go public. Double check the quotes and verify their source.

Overview of changes:

• Work page now has links to case studies. If there is no link, case study is just a block with no button.
• Hero has been tweaked so the video is the correct hex of pebble pink
• Tweaked images across pages to improve focal point
• Vectorised and refactored illustrations
• Refactored verticals js – simplified
• Refactored contact page, removed tabs completely from the site

Up next:

• Addition of the Bede case study, but I think we can push this pull request and add Bede in with later commit to master.