Filter mappings by New URL

This needs some attention from @fofr for the spacing of the radio buttons.

It's worth noting that, just like the "Original path" filtering this does partial matches, so a filter of: `https://www.gov.uk/government/organisations/department-for-work-pensions/about` will match:
```
https://www.gov.uk/government/organisations/department-for-work-pensions/about
https://www.gov.uk/government/organisations/department-for-work-pensions/about/our-energy-use
https://www.gov.uk/government/organisations/department-for-work-pensions/about/equality-and-diversity
```