Add option to mark multiple selected workflows as active/inactive

[Dave Lebbing]

Example: select multiple workflows and choose “Mark active” or “Mark inactive” from the File menu. This would make it easier when saving a subset of workflows to volume or dmg.

Also good if there were keyboard shortcuts for this:

“command-a” for mark active

“command-shift-a” for mark inactive

[Dave Lebbing]

Duplicated in issue #253