Allow custom restart pollInterval and quietPeriod

Allow the pollInterval and the quietPeriod of the filewatcher to be
configured.

Fixes gh-3139

spring-boot-samples/spring-boot-sample-devtools/src/main/java/demo/SampleDevToolsApplication.java

@@ -26,5 +26,4 @@ public class SampleDevToolsApplication extends WebMvcAutoConfigurationAdapter {
 	public static void main(String[] args) {
 		SpringApplication.run(SampleDevToolsApplication.class, args);
 	}
-
 }

spring-boot-samples/spring-boot-sample-devtools/src/main/resources/application.properties

@@ -1,2 +1,3 @@
 spring.devtools.remote.secret=secret
+# spring.devtools.restart.poll-interval=10000
 # spring.devtools.restart.trigger-file=.reloadtrigger