Update button wording to indicate publish

* When a stats announcement is created, edited or has its date changed,
the changes are immediately published — the button text needs to make
this clear
Apply form-large styles to date change form
Cleanup stats announcements list

* Put header at the top of the page
* Move warning down and give better vertical spacing to create
announcement action
* Rename search to filter to match other filter forms on Whitehall
* Make the search button a Bootstrap styled button
Port table header styles from admin template

* Add table example to style guide
* Include styles for table header and secondary table headers
Apply ported table styles to stats listing

* Give the table a prominent header consistent with other admin apps
Port and apply no content styles from admin gem

* A large but light style which applies to the empty state.
* Apply when no statistics announcements are found by a filter
Cleanup stats announcement page

* Indicate statistics type above title, matching front-end
* Clarify the view on website link, specifying which site
* Remove the warning message and fix grid layout of page
* Format details and summary in the same style as used on the front-end
* Remove delete announcement button
Cleanup document linker

* Delete existing overrides and inline styles
* Update language from “linking” to “connecting” to avoid confusion
related to behaviour of legacy systems, as observed in user research
* Re-style document finder, which uses IDs for styles and javascript
which makes refactoring or overriding styles difficult
Make stats forms more mobile friendly

* Using span8 grid classes meant that form elements were always a
percentage width of the viewport, at small widths this doesn’t make
sense
* Use max-widths instead, the form expands up to a certain point, but
on smaller viewports elements take up more of the limited screen space
* Apply the same logic to organisation and topic selects