R1:fcad9435ea82

Allow Almanac Devices and Bindings to have properties

Summary:
Ref T5833. Adds support for arbitrary properites to Almanac devices and bindings.

- For Devices, this allows you to maybe mark what `rack` a server is on, the `serial` number of a router, etc.
- For Bindings, this allows you to maybe mark that a bound device is `active`, provide `credentials`, expose it as `readonly`, etc.

Test Plan: Added properties to Devices and Bindings.

Reviewers: btrahan

Reviewed By: btrahan

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