R1:ea9187ea92ec

Allow Almanac properties to be set and deleted via Conduit

Summary:
Depends on D19342. Ref T12414. Ref T13120. This adds an EditEngine extension for editing Almanac properties.

The actual wire format is a little weird. Normally, we'd have a transaction for each property, but since you can pick any property names you want we can't really do that (we'd have to generate infinite transactions).

The transaction wire format anticipates that transactions may eventually get some kind of metadata -- each…