FEATURE: allow "uncheck all" on filters in workflow

[ewhitley]

In the "workflows" "filters", consider how we might allow an "uncheck all" type of operation.

I'm lazy and don't want to uncheck all of the checkboxes just so I can check 'data' :)

[lrasmus]

This makes perfect sense! In thinking about how to implement this, I'm realizing that I probably implemented the filtering backwards - which is contributing to this problem.

By default all of the filters are checked - meaning "on". Unchecked means "hide assets that match this attribute". I believe most other filters start with everything unchecked, then as you check it means "show me just items that match the checked attributes".

@ewhitley - do you think we should switch the behavior so that all filters are unchecked by default, and checking an item means to filter to show only that particular type of item?