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
