sync index list filter page headers and forms
tweaking header sizes and tidying input size and display

https://www.pivotaltracker.com/story/show/44128453
adding placeholder text no js fallback yet
moving js-filter-form to a helper to be shared across the 3 pages

https://www.pivotaltracker.com/story/show/44128453
Revert "moving js-filter-form to a helper to be shared across the 3 pages"

This reverts commit 956aa953c725de7f72348eaa1b197457e36b4863.
moving js-filter-form to helper so that it can be shared
moving js-filter-form to index-list.scss
h1 indent fix
Merge pull request #354 from alphagov/index-list-filter-update

Index list filter update

https://www.pivotaltracker.com/story/show/44128453