We had 7 classes in _grids.scss named `.column-...` which were being
used to give a certain column width. These worked by using `@include
grid column()`, which is now deprecated.
`.column-whole` and `.column-three-quarters` can be removed and replaced
with `govuk-grid-column-full` and `govuk-grid-column-three-quarters`
respectively. The other column classes don't have a direct replacment in
GOV.UK Frontend. To get round this, we overwrite the `$govuk-grid-width`
SASS map in `extensions.scss` to add in extra widths, then use this with
the `govuk-grid-column` mixin to create new classes in for our custom
widths in `_grids.scss`
Pages within a service use a 2/8, 5/8, 1/8 grid.
The content pages use a 1/4, 3/4 grid, for consistency with the product
page template.
But I feel like the internal consistency is more important, and it feels
weird for the main content column to jump about.
