LMS-187 Making the 'Department' on the front cover persistent

Summary of feature request

Add Department to Document Summary information and create placeholder in the explanatory note on the front cover of a Bill, so that it is persistent when replacing the front cover.

Original user description

At the moment, you have to manually type in the Department name into the explanatory notes section of the front cover of a Bill. This means that when you insert a new front cover, the Department is wiped blank. That can be a trap if you, eg, use the finalise version function from the project page (which caught me out recently on a Bill I was preparing for introduction when I had to update the front cover to reflect a change in the Bill minister). Could a box for the Department be added to the ‘Document Information’ page, perhaps alongside Members, so that it becomes persistent in the same way that the Bill presenter is?