Remove one level of indentation
Remove one level of indentation

I'm trying to restructure the css a bit to make it easier to add new input types to it when required. This commit de-nests some of the SCSS to make it easier to read.
Take .filter, .radio-filter, .checkbox-filter and .text-filter out of .filter-form scoping.

alphagov/finder-frontend,alphagov/finder-frontend,alphagov/finder-frontend,alphagov/finder-frontend