Add Implementation-Version entry to MANIFEST.MF

e.g.:

    Implementation-Title: spring-core
    Implementation-Version: 3.2.0.BUILD-SNAPSHOT

Setting these values is good as a general practice, but required in
order to support the functionality in spring-core's SpringVersion class.

build.gradle

@@ -48,6 +48,9 @@ configure(subprojects) { subproject ->
     apply from: "${rootProject.projectDir}/publish-maven.gradle"
 
     jar {
+        manifest.attributes['Implementation-Title'] = subproject.name
+        manifest.attributes['Implementation-Version'] = subproject.version
+
         from("${rootProject.projectDir}/src/dist") {
             include "license.txt"
             include "notice.txt"