Add setIgnoreDefaultModelOnRedirect support

Add a `spring.mvc.set-ignore-default-model-on-redirect` property to
allow RequestMappingHandlerAdapter.setIgnoreDefaultModelOnRedirect to
be easily customized and change the default value to 'true'.

Fixes gh-2018

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

@@ -87,6 +87,7 @@ content into your application; rather pick only the properties that you need.
 	spring.mvc.locale= # set fixed locale, e.g. en_UK
 	spring.mvc.date-format= # set fixed date format, e.g. dd/MM/yyyy
 	spring.mvc.message-codes-resolver-format= # PREFIX_ERROR_CODE / POSTFIX_ERROR_CODE
+	spring.mvc.ignore-default-model-on-redirect=true # If the the content of the "default" model should be ignored redirects
 	spring.view.prefix= # MVC view prefix
 	spring.view.suffix= # ... and suffix
 	spring.resources.cache-period= # cache timeouts in headers sent to browser