[DataAccess] Allow resizing of master/detail split panel #123
Description
Currently the master/detail split panel (shared across tabs) is of a fixed height and width. The UX spec calls for it to be resizable--at least--in the vertical direction.
This task is split from the original master/detail work #109 as this is a fairly isolated task (and arguably of a different priority).
(I experimented with a couple of the popular React libraries that provide split-panel components, but wasn't able to get them to work satisfactorily, either because they make assumptions about the height/width requirements of their parent and ancestor components or because they're dependent on later versions of react.)