Restructured tri-layout grid system, so the sidebars are contained in
their own child grid system, mimicking the parent grid, so we can treat
them as part of the same parent scroll container at smaller screen
sizes for consistent scroll/sticky behavior.
Tested on Firefox, Chromium, Gnome Web and Safari (MacOS).
For #4394
Changes made during review of #4562
Would cause effect where scroll area would be cut of by spacing which
looked a bit strange. This retains the same padding sizes but cuts the
content at the header or top of viewport.
- Primarily moved and re-organised view files.
- Included readme within views to document the convention.
- Fixed some issues with page field select list in previous commit.
- Tweaked some route names while going through.
- Split some views out further.
Closes#2805
