Search box for both types of URI lookups

[aclarkxyz]

Currently when in "Lookup" mode for an assignment (whether property or value), there are two tabs: List and Hierarchy. Only the first one shows a search box:

The hierarchy view doesn't have one - though it is possible to search using the other tab and then switch between them:

To do: add a searchbox to the Hierarchy tab, and make it possible to locate a term of interest by typing in content. It is currently possible to use the List tab to search for a term and then switch to the Hierarchy tab and see the selection preserved, but this isn't ideal... it would be nicer to be able to just type in content in the same tab, and see the selection update accordingly.