R1:25e7b7d53cd5

Implement support for creating and updating fragments from ZIPs

Summary:
This implements support for creating and updating fragments from ZIP files. It allows you to upload a ZIP via the Files application, create a fragment from it, and have it recursively imported into Phragment. Updating that folder with another ZIP will recursively create, update and delete files as appropriate.

The logic for creating and updating fragments from files has also been centralized into the PhragmentFragment class.