goat: add ability to upload all blobs in a folder

[ledlamp]

The goat blob export command downloads all blobs of an account into a folder.

The goat blob upload command only accepts one file.

It should accept multiple file arguments, which could be filled by shell glob.

Or it should accept a path to a folder, because there may be too many blobs to put into arguments.

This would be useful for manual PDS migrations.

[bnewbold]

You could use parallel to call goat once for every file in a folder, at least for now.

[ledlamp]

I've been using this on windows

Get-ChildItem | ForEach-Object { goat blob upload $_ & }

but it's really inefficient, makes windows defender use all the cpu, each goat makes a request to refreshSession