Prefix the json pointer reference with the schema id.

Ensure that two local json pointers in two different schemas will use their own definition that they point to,
and not the one that was loaded first.
Fixes #182

Author: vierbergenlars

core/src/main/java/org/everit/json/schema/loader/ReferenceLookup.java

@@ -115,13 +115,14 @@ private JsonObject lookupObjById(JsonValue val, String idAttrVal) {
     }
 
     private Schema.Builder<?> performQueryEvaluation(String mapKey, JsonPointerEvaluator pointerEvaluator) {
-        if (ls.pointerSchemas.containsKey(mapKey)) {
-            return ls.pointerSchemas.get(mapKey);
+        String absolutePointer = ReferenceResolver.resolve(ls.id, mapKey).toString();
+        if (ls.pointerSchemas.containsKey(absolutePointer)) {
+            return ls.pointerSchemas.get(absolutePointer);
         }
         JsonValue rawInternalReferenced = pointerEvaluator.query().getQueryResult();
         ReferenceSchema.Builder refBuilder = ReferenceSchema.builder()
                 .refValue(mapKey);
-        ls.pointerSchemas.put(mapKey, refBuilder);
+        ls.pointerSchemas.put(absolutePointer, refBuilder);
         Schema referredSchema = new SchemaLoader(rawInternalReferenced.ls).load().build();
         refBuilder.build().setReferredSchema(referredSchema);
         return refBuilder;