Replaced `$gutter` and similar variables such as `$gutter-half` with the
`govuk-spacing()` static spacing function. This uses `govuk-spacing()`
instead of `$govuk-gutter` because `$govuk-gutter` should only be used
for the gaps in between grid columns and we were mostly using `$gutter`
to add more space around elements.
There are other places in the SCSS files where we had hardcoded a
measurement in px which could be replaced with `govuk-spacing`, but this
commit only replaces the existing uses of `$gutter`.
Our usage for these browsers in the last month is down to 0.2% of all
users, or 14 individual users, according to Google Analytics.
These users also visit about half the number of pages per sessions,
suggesting that they’re not signed in.
Expands the API of the macro to allow nested
checkboxes to have a summary tracking the current
selection, the fieldset to expand/collapse and
buttons to be added to allow jumping between
states.
Includes making 'Done' button inline on mobile.
Helps differentiate it form the form submit.
