fix articles page sort, filter, search

[StephDriver]

closes #5464
closes #5471

[StephDriver]

These changes are all about the articles page.

• fix a bug in OLH that meant the sort wasn't working.
• improve accessibility so that page is compatible with keyboard and screen reader
• improve accessibility (readability) by changing button labels to sort, filter and search instead of a mix of apply and those terms. Nice and clear which one applies which.
• changes css so that the clear all and apply all buttons in the filter are quieter than the filter itself.
• tweak css so that the elements within the sort block are neatly aligned (as previously in Clarity, but not great in other themes).

Added two template tags

• one is for including aria in form fields - this was needed to make the date fields screen reader compatible, but is likely to be useful elsewhere. A template tag is needed because you need to pass in the relevant ID to the relevant field, and hte id may only be known through loops of the calling template, i.e. not static.
• other is for adding ids that aren't duplicates to elements that otherwise would be duplicated due to the way they are generated (e.g. in a loop). IDs being needed for describedby and labelledby but also needing to be unique on the page for valid HTML.