Passing entity store object to the entity selector widget

If available, an entity store can be passed to the entity selector to be able to gather any entity
data from.

- patch set 2: Passing entity store instead wikibase object as option

Change-Id: I22d65d7ac804a7c2455704d3c7a1619438c6c75e
Merge "Passing entity store object to the entity selector widget"