[Feature] Majority of fields should be optional when updating edge rule

[ToshY]

When testing noticed that the addOrUpdateEdgeRule both handles add and update and has several required keys set, but the majority of those are only relevant for adding a new rule. Updating a rule only seems to require the Guid and atleast 1 Triggers (else it results in {"ErrorKey":"edgerule.invalid","Field":"EdgeRule","Message":"At least one condition is required"}).

Originally posted by @ToshY in #135 (comment)