Additional changes to index.html

[sdwilkes]

Hi @punalsc , just logging these changes for reference:

• [x] Change 'Search the catalogue' to 'Search our catalogue' in the Discovery card
• [x] Remove 'Our catalogue' from 'Useful links' card
• [x] Add 'The National Archives' main website' to 'Useful links' card
• [x] Link the TNA logo in header to the TNA homepage
• [x] Update What's on banner to the full Henry VIII version
• [x] Add 'All online records' to 'Online records' card
• [x] Add the standard Beta banner
• [x] Privacy policy to open in a different window _blank
• [x] Update the introduction for Search our catalogue
• [x] Change title on reader's screen page
• [ ] Remove the 'Contact us' box