LHCb: DOI and more in `lhcb-derived-datasets.xml`

* Adds DOI and accelerator/experiment fields in
  `lhcb-derived-datasets.xml`.  (addresses #145) (PR #539)
UI: updates to final homepage

* makes “home2” the portal’s homepage
* removes pages under “/home$”
* "latest" -> "genuine" (closes #549)
search: updates search result page

* standardise the tags in the record brief (closes #544)
* moves DOI tag on brief-footer
* makes brief-header wider for better title display
* makes search-results-header more responsive
records: updates record templates

* fixes “citation recommendation” format
* moves preview after description field (closes #546)
* “export” moves to the end of the page (addresses #545)
UI: updates "CMS physics page" / menu + collapse

* collapsing/expanding "things-to-remember"
* fixes styling in “Content” menu
* (closes #518)
UI: removes news section

* (closes #542)
UI: homepage updates in text and navigation

* adds exp “short” description in fixtures
* adds exp “short” descriptions to home boxes
* makes the whole experiment box clickable
* disables click for ALICE, ATLAS, LHCb in research section
UI: centers homepage image