Add (back) 'Show Branches as Tree' toggle, for consistency and convenience

[goran-w]

It would be more consistent (and equally useful) to have a toggle-button Show Branches as Tree for LOCAL BRANCHES and for the branches under each of the top-levels under REMOTES, just like there are corresponding toggle-buttons for TAGS and SUBMODULES.

Since a "flat" view is sometimes preferred, it ought to be equally available for all these categories.