Add Gradle extension (ext) definitions to override the Spring Framework and Spring Data versions.

build.gradle

@@ -14,6 +14,9 @@ apply plugin: 'io.spring.convention.root'
 group = 'org.springframework.data'
 description = 'Spring Test Framework for Apache Geode and Pivotal GemFire using Spring Data.'
 
+//ext['spring.version'] = "$springVersion"
+//ext['spring-data-releasetrain.version'] = "$springDataReleaseTrainVersion"
+
 ext.releaseBuild = version.endsWith('RELEASE')
 ext.snapshotBuild = version.endsWith('SNAPSHOT')
 ext.milestoneBuild = !(releaseBuild || snapshotBuild)