Draft: Added corrects method on EconomicEvent

Added a recursive from EconomicEvent to another EconomicEvent when the first event requires a correction or needs to be backed out completely. Negatives are allowed on quantities in this case.

This can also be used when a number of events need to be combined into one visually, such as in the time clock start/stop app.

NOTE: I added the property to the initial EconomicEvent definition, did not add anywhere else.

lib/schemas/observation.gql

@@ -57,8 +57,8 @@ type EconomicEvent {
   "References another economic event that implied this economic event, often based on a prior agreement."
   triggeredBy: EconomicEvent
 
-  "The economic event can be safely deleted, has no dependent information."
-  deletable: Boolean
+  "Used when an event was entered incorrectly and needs to be backed out or corrected. (The initial event cannot be changed.)"
+  corrects: EconomicEvent
 
   # inverse relationships and queries
 
@@ -69,6 +69,9 @@ type EconomicEvent {
   next: [ProductionFlowItem!]
   track: [TrackTraceItem!]
   trace: [TrackTraceItem!]
+
+  "The economic event can be safely deleted, has no dependent information."
+  deletable: Boolean
 }
 
 """