Revamp Home; Remove About sidebar; Redirect contact and get pages

[PhilReedData]

Raised in #14, I have made the following changes to the SEEK docs: home pages and About pages. These pages mostly did not describe what SEEK is About, it was not the best name.

• Home: Reorganised, removed legacy content and the banner graphic. Added simple icons to the popular pages tiles. Included the content of the 'Get FAIRDOM-SEEK' page in a neater, more compact way.
• Get FAIRDOM-SEEK: Moved content to Home page (see point above). Redirect the /get-seek path there as it appears on other sites.
• Contacting us: This content is mostly already covered on the FAIRDOM Contacting us page, except the support@ email address. Put a redirect to the FAIRDOM page. Several docs pages link to the contact page, leave them unchanged and let the redirect handle things.
• Credits: This page is likely out-of-date (check with @stuzart). Keep the link to it in the site footer. Remove the sidebar.
• Delete the About sidebar.
• Tweak the <hr> style in main content.

What impact does this have for DataHub docs?

[kdp-cloud]

I like it. The home page much leaner than before. I also like the fact that the popular pages section has moved to the top.
For the DataHub docs, we always said to use the FAIRDOM-SEEK docs as base and just put our DataHub specific content on top of FAIRDOM-SEEK's. So no blockers on our side. I'm just tagging in @NielsGeudens to give his opinion as well.
Just one remark / question. the get-seek and contacting-us page our not accessible anymore. Should we make a plan to remove this content in the future?