filesystem find_one not completed

[sl5035]

1. address the comments and I will merge this
2. work on find_one have it take a db, a collection and a filter and have it return a document/dict. This is the most general case. This is the general signature of find_one
3. in the fs client, have it do this on a json serialized version of the cifs. Zach wrote code to do this serialization. To reduce effort, just use his serialization, we don't have to reinvent it. For the test, make a tmpfile and write two cif jsons in there and test that it gets the right one. For a better test, filter on something that we might filter on in the real case (something like ciffile name or sthg)

We need to bite the bullet and build the runcontrol infrastructure too. To keep things simple, make runcontrol to be a dict and pass in what we need. Use the Schema in Regolith (databases and so on). Later we may want to import runcontrol from regolith and reuse all the nice things but that will add a lot of bloat to the dependencies (gooey etc. that we won't be using).

Then we can merge that branch. Then we want to refactor the front-end to use the client, so replace the load_cifs() or whatever with a loop that calls find_one resetting the filter in each iteration of the loop. that can be on a separate branch. It won't need new tests, but all the old tests should still pass when it is working.

and so on....

Originally posted by @sbillinge in #146 (comment)