Rework staging area directory structure

[kMutagene]

• [ ] name in the folder, name and version in the filename:

  src/PackageRegistryService/StagingArea/
  ├─ package-name/
  │  ├─  package-name@1.0.0.fsx
  │  ├─  package-name@1.1.0.fsx
  │  ├─  package-name@2.0.0.fsx

  reflect location changes in this repo:

• [x] update-index.fsx
• [x] pre-commit hook
• [x] DB seeding for local dev
• [x] Github API based access via arc-validate