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

Subscribers: epriestley

Maniphest Tasks: T5833

Differential Revision: https://secure.phabricator.com/D10781