Added option to disable introspection query (fix #124)

Depends on graphql-java-tools v5.3.4

Author: oliemansm

gradle.properties

@@ -40,7 +40,7 @@ LIB_GRAPHQL_JAVA_VER = 9.2
 LIB_JUNIT_VER = 4.12
 LIB_SPRING_CORE_VER = 5.0.4.RELEASE
 LIB_SPRING_BOOT_VER = 2.0.5.RELEASE
-LIB_GRAPHQL_SERVLET_VER = 6.2.0-SNAPSHOT
+LIB_GRAPHQL_SERVLET_VER = 6.1.4
 LIB_GRAPHQL_JAVA_TOOLS_VER = 5.3.4-SNAPSHOT
 LIB_COMMONS_IO_VER = 2.6