Remove formats from sector pages, replace with sector name

Remove the "Specialist topic" label from industry sector browse pages, 
and replace them with the name of the sector on subcategory pages.
Strip the sector name from artefact titles

When the name of an artefact begins with the name of the sector (eg. 
"Oil and gas: wells"), strip the sector from the title and upcase the 
first character of the remaining string.
Merge pull request #506 from alphagov/industry-sector-browse-tweaks

Industry sector browse tweaks