Externalize H2 database dependency version

gradle.properties

@@ -21,3 +21,4 @@ assertjVersion=2.3.0
 spockVersion=1.0-groovy-2.4
 jstlVersion=1.2.1
 groovyVersion=2.4.4
+h2Version=1.4.191

samples/httpsession-jdbc-xml/build.gradle

@@ -9,7 +9,7 @@ sonarqube {
 dependencies {
 	compile project(':spring-session-jdbc'),
 			"org.springframework:spring-web:$springVersion",
-			"com.h2database:h2:1.4.191",
+			"com.h2database:h2:$h2Version",
 			jstlDependencies
 
 	providedCompile "javax.servlet:javax.servlet-api:$servletApiVersion"

samples/httpsession-jdbc/build.gradle

@@ -9,7 +9,7 @@ sonarqube {
 dependencies {
 	compile project(':spring-session-jdbc'),
 			"org.springframework:spring-web:$springVersion",
-			"com.h2database:h2:1.4.191",
+			"com.h2database:h2:$h2Version",
 			jstlDependencies
 
 	providedCompile "javax.servlet:javax.servlet-api:$servletApiVersion"

spring-session/build.gradle

@@ -28,7 +28,7 @@ dependencies {
 	integrationTestCompile "redis.clients:jedis:2.4.1",
 			"org.apache.commons:commons-pool2:2.2",
 			"com.hazelcast:hazelcast-client:$hazelcastVersion",
-			"com.h2database:h2:1.4.191"
+			"com.h2database:h2:$h2Version"
 
 	integrationTestRuntime "org.springframework.shell:spring-shell:1.0.0.RELEASE"