Moved creature variables to their own collection

Another big change to the engine, expect bugs

app/imports/api/creature/creatures/CreatureVariables.js

@@ -0,0 +1,21 @@
+//set up the collection for creature variables
+let CreatureVariables = new Mongo.Collection('creatureVariables');
+
+// Unique index on _creatureId
+if (Meteor.isServer) {
+  CreatureVariables._ensureIndex({ _creatureId: 1 }, { unique: true })
+}
+
+/** No schema because the structure isn't known until compute time
+ * Expect documents to looke like:
+ * {
+ *   _id: "nE8Ngd6K4L4jSxLY2",
+ *   _creatureId: "nE8Ngd6K4L4jSxLY2", // indexed reference to the creature
+ *   explicitlyDefinedVariableName: {...some creatureProperty}
+ *   implicitVariableName: {value: 10},
+ *   undefinedVariableName: {},
+ * }
+ * Where top level fields that don't start with `_` are variables on the sheet
+**/
+
+export default CreatureVariables;