DataSelection: Show exception on terminal, not just in a popup window.
DataSelection: Added convenience function configureRoleJson()
shell: Deleted an unused function.
DataSelection:
- DatasetInfo now has subvolume_roi attribute, which some data formats may use to specify a roi before the data is even loaded.
- Added modifications to the standard DVID browser UI to allow selection of the desired roi.
DataSelection: subvolume_roi attribute can be loaded from json. Also, store the subvolume_roi in the output metadata.
Applet: Added a busy flag.  See also: issue #789
shell: If the currently selected drawer is disabled, disable the drawer contents.