Add auto-configuration support for Spring Session

This commit adds support for automatically configuring Spring Session.
In a web application when both Spring Session and Spring Data Redis
are on the classpath, Spring Session's Redis Http Session support
will be auto-configured. The max inactive interval for Redis-backed
sessions can be configured via the environment using the existing
server.session-timeout property.

Closes gh-2318

spring-boot-samples/spring-boot-sample-session-redis/pom.xml

@@ -0,0 +1,48 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<parent>
+		<!-- Your own application should inherit from spring-boot-starter-parent -->
+		<groupId>org.springframework.boot</groupId>
+		<artifactId>spring-boot-samples</artifactId>
+		<version>1.3.0.BUILD-SNAPSHOT</version>
+	</parent>
+	<artifactId>spring-boot-sample-session-redis</artifactId>
+	<name>Spring Boot Session Redis Sample</name>
+	<description>Spring Boot Session Redis Sample</description>
+	<url>http://projects.spring.io/spring-boot/</url>
+	<organization>
+		<name>Pivotal Software, Inc.</name>
+		<url>http://www.spring.io</url>
+	</organization>
+	<properties>
+		<main.basedir>${basedir}/../..</main.basedir>
+	</properties>
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-web</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-redis</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.session</groupId>
+			<artifactId>spring-session</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-test</artifactId>
+			<scope>test</scope>
+		</dependency>
+	</dependencies>
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.springframework.boot</groupId>
+				<artifactId>spring-boot-maven-plugin</artifactId>
+			</plugin>
+		</plugins>
+	</build>
+</project>