revamped structure of /index.html

TODO: disperse content from /home/index.html into other pages; then
delete.
updated intro content to each 'portal' page, moved files

TODO:
- finish ‘portal’ pages content, and for fuck sake get rid of the
`<details>` elements!
rewrote all portal pages HTML
fixed breadcrumbs concept

TODO: merge breadcrumb styles into `design` branch
added support; updated todo
Merge branch 'homepage' into design