Change default schema location to /graphql/schema.graphqls

This commit changes the default location for the GraphQL schema from
`classpath:schema.graphqls` to `classpath:/graphql/schema.graphqls`.

We're also adding `.graphqlconfig` files that are leveraged by a GraphQL
JS plugin in IntelliJ IDEA.

Closes gh-44

graphql-spring-boot-starter/src/main/java/org/springframework/graphql/boot/GraphQLProperties.java

@@ -52,7 +52,7 @@ public class GraphQLProperties {
 		/**
 		 * Location of the GraphQL schema file.
 		 */
-		private String location = "classpath:schema.graphqls";
+		private String location = "classpath:graphql/schema.graphqls";
 
 		private final Printer printer = new Printer();