Arvados

I would like to understand better:

• How does a specified limit restrict the Collections chosen? Does Workbench show every Collection with at least one matching file? Every Collection where all the files match? Every Collection that has exactly one file that matches?
• Should the component be able to specify more than one limit? If so, do we AND or OR those limits?
• What format(s) do we want to support for limits? Simple strings, shell globs, regular expressions, something else?

This story is just a channel between the pipeline author and the search box in the collection chooser: the desired search behavior is "whatever the collection chooser would do if you typed that string in the search box yourself".

Making better search operators is a worthwhile but separate story. As the search box becomes more capable, that benefit will automatically extend to this scenario. But we can play with it on the Workbench side. I don't want to overthink this before we have some more real-life examples. (Then I'll want to overthink it.)

At c28309c, LGTM.