should be able to include non-R scripts in scripts

[aappling-usgs]

viz items have a scripts section that gets special handling (extraction of the relevant functions into another ~hidden file that includes just those functions necessary for that viz item). this section is supposed to support re-building of the viz item if any of the relevant functions have been edited. it would be great if this section also worked for non-R scripts - in my current use case in water-use-15, that's an .sh bash script, but could also by python, etc.. It doesn't work for non-R scripts now because of the special and R-specific handling, which means that when I edit the .sh file (which I've named as its own non-depends, non-script argument) i need to remember to remake::delete the target to force a rebuild. i can't put the .sh file in scripts because the R handling breaks. i can't put the .sh file in depends without making a viz item, reader, and fetcher/processor/somethingor for it, which seems like a big pain, so i think the manual deletion is the best option we have right now. a still better option would be for vizlab to support non-R scripts in scripts.