Industry sector browse tweaks

This pull request makes some changes to the industry sector browse pages. Specifically, this:

- removes the 'specialist topic' format label from the browse pages.
- adds the sector name (eg 'Oil and gas') in place of the format label on subcategory pages, so that topics with generic-sounding names like 'Licensing' will appear with context of their parent category.
- strips the sector name from artefacts with titles containing the sector (eg. 'Oil and gas: wells' becomes 'Wells').