dumpling cli planning

At the moment we have two downzip functions. Ideally we should unify and have an agreement as to what downzip does. At the moment, corezip is the python function that zips up the contents on the lab machine and then uploads to blob storage, and downzip does the downloading and unzipping of the contents.

@schaabs does corezip take care of uploading? Perhaps downzip could just be split in to two: One is the downloading piece, then the unzipping + locating core files logic?

in other words, convert downzip in to:
def DownloadZip(...)
def CoreUnzip(...)

Updates
We riffed on this a bit.

In addition to the two-apis listed above, we'd also have:

def UploadZip(...)
def CoreZip(...)

We'd place them in to dumpling.py which lays a foundation for dumpling CLI.