batches: add basic library pane for SSBC editor
Created by: courier-new
Adds back the minimal example specs to choose from when writing a new batch spec, and a confirmation modal so that you don't accidentally erase your editor contents if you select one by accident.
Ignore the drawer UI... Our version of reactstrap's Collapse only does up/down collapsing, not left/right, and trying to upgrade the package breaks our tooltips and a handful of other things.