DSL: Mail namespace & MailSendingMessageHandler

DSL:Add SMTP Mail Server

Polishing - PR Comments

DSL: Mail: add `PropertiesConfigurer` lambda

* Move `IntegrationFlowTests` to the `flows` package to avoid cross scanning for components
* Make `MailTests` as integration test and move `Mail.outboundAdapter` to the `IntegrationFlow` `@Bean` definition

spring-integration-java-dsl/build.gradle

@@ -30,6 +30,7 @@ ext {
 	ftpServerVersion = '1.0.6'
 	jacocoVersion = '0.7.1.201405082137'
 	jmsApiVersion = '1.1-rev-1'
+	mailVersion = '1.4.7'
 	slf4jVersion = '1.7.7'
 	springIntegrationVersion = '4.0.3.RELEASE'
 	springBootVersion = '1.1.5.RELEASE'
@@ -78,6 +79,7 @@ dependencies {
 		compile("org.springframework.integration:$it:$springIntegrationVersion", optional)
 	}
 	compile ("javax.jms:jms-api:$jmsApiVersion", provided)
+	compile ("javax.mail:javax.mail-api:$mailVersion", provided)
 
 	testCompile "org.springframework.integration:spring-integration-test:$springIntegrationVersion"
 	testCompile "de.flapdoodle.embed:de.flapdoodle.embed.mongo:$embedMongoVersion"
@@ -90,6 +92,8 @@ dependencies {
 	testRuntime("org.apache.activemq:activemq-kahadb-store:$activeMqVersion") {
 		exclude group: "org.springframework"
 	}
+	testRuntime "com.sun.mail:mailapi:$mailVersion"
+	testRuntime "com.sun.mail:smtp:$mailVersion"
 
 	jacoco "org.jacoco:org.jacoco.agent:$jacocoVersion:runtime"
 }