Allow Almanac service types to define default properties
Summary:
Ref T5833. This allows Almanac ServiceTypes to define default properties for a service, which show up in the UI and are more easily editable.
Overall, this makes it much easier to make structured/usable/consistent service records: you can check a checkbox that says "prevent new allocations" instead of needing to know the meaning of a key.
Test Plan: {F251593}
Reviewers: chad, btrahan
Reviewed By: btrahan
Subscribers: epriestley
Maniphest Tasks: T5833
Differential Revision: https://secure.phabricator.com/D10996