Add load-on-startup property to DispatcherServlet

Closes gh-2481

spring-boot-docs/src/main/asciidoc/appendix-application-properties.adoc

@@ -337,6 +337,7 @@ content into your application; rather pick only the properties that you need.
 	spring.mvc.locale= # Locale to use.
 	spring.mvc.media-types.*= # Maps file extensions to media types for content negotiation.
 	spring.mvc.message-codes-resolver-format= # Formatting strategy for message codes. For instance `PREFIX_ERROR_CODE`.
+	spring.mvc.servlet.load-on-startup=-1 # Load on startup priority of the Spring Web Services servlet.
 	spring.mvc.static-path-pattern=/** # Path pattern used for static resources.
 	spring.mvc.throw-exception-if-no-handler-found=false # If a "NoHandlerFoundException" should be thrown if no Handler was found to process a request.
 	spring.mvc.view.prefix= # Spring MVC view prefix.