Steam preservation proposal

folder structure (top level folder = dat entry):
```
app1
  depot1
    CSM/CSD with all depot chunks
    all depot manifests
    depot key
  depot2
    ...
  possibly sidecar file with update history (for correct manifest combos). current manifest combos can be retreived via steam. could include historical data from steamdb, marked as such.
```

chunks and manifests are to be the raw files from the server

when a new manifest is pushed, the CSM/CSD file would be updated (added as new file, with old file excluded from DoM?) and new manifest file added

unsolved issues:
* tooling to automate all this

supplemental projects:
* Steam1 and Steam2 data (current Steam is Steam3)
* recording app and package info, so that "trap DLC" DRM can be avoided and the real steam install process can be recreated (rather than user manually choosing depots)
* recording achievement info, so that can be used offline with steam emulators
* SmartSteamEmu is closed source and windows only (its apparently the best steam emulator - hooks API calls instead of replacing DLLs, has achievement display)
* recording the rest of the metadata on steam