Make a collection in the database

[stevenhua0320]

1. make a collection locally (a file called packages.yml in your db directory) and put a couple of packages in there. For now, let's use diffpy.utils and diffpy.pdfmorph which we just released. Just use PyCharm to do it.
2. Make a couple of UCs for what kind of searches we will do on these. I suggest that we make a lister-helper first that makes queries to that db and collection and returns things. We can discuss what, but it will be things like "Simon wants to know all the packages that the group released in the last year", things like that.
3. Decide what info we want printed to the screen. Ususally we want a verbose and non-verbose choice, where the latter is summary info, one line per package and the verbose has much more. Look in the other listers for ideas.
4. Make a lister that does this. First write a test that has the output in a format that we want, then write the function to go and get the info and print it like that.

[stevenhua0320]

UC1: Simon wants to know all the packages that the group released in the last year.
UC2: Simon wants to know all the packages that released by the the target authors.
UC3: Tina wants to know all the packages that have the same "function label".
UC4: Andrew knows the packages that want to generate the report, but he wants to know the content after the third time release.
UC5: Simon wants to know about dependencies between the packages.