Improved hierarchy expand functionality

Allow us to 'expand all down one level in the hierarchy' after 'go to the next level in the hierarchy'. Currently, the expand option greys out when you haven't been expanding from the top level but it's still possible to drill down.

Example hierarchy for chemical industry:
Product market sector
Product formulation
Product
Pack Size

You currently can't drop to the Product level and then expand to Pack Size without removing levels (which someone who's using shared content can't do).