Add specification version to jars, and impl-title/version & spec vers… (

#533)

* Add specification version to jars, and impl-title/version & spec version to javadoc and sources jars

Signed-off-by: Gary Brown <gary@brownuk.com>

* Refactored to have shared manifest in publish.gradle

Signed-off-by: Gary Brown <gary@brownuk.com>

* New improved approach thanks to @jpkrohling

Signed-off-by: Gary Brown <gary@brownuk.com>

build.gradle

@@ -74,9 +74,6 @@ subprojects {
 
     jar {
         from sourceSets.main.output
-        manifest {
-            attributes('Implementation-Title': project.name, 'Implementation-Version': project.version)
-        }
     }
 
     if (!version.endsWith("SNAPSHOT")) {
@@ -192,6 +189,11 @@ configure(subprojects.findAll {it.name != 'jaeger-thrift'}) {
         // These are disabled because of a bug with errorprone. See https://github.com/google/error-prone/issues/750
         options.compilerArgs += [ '-Xep:NestedInstanceOfConditions:OFF',  '-Xep:InstanceOfAndCastMatchWrongType:OFF' ]
     }
+    tasks.withType(Jar) {
+        manifest {
+            attributes('Implementation-Title': project.name, 'Implementation-Version': project.version, 'Specification-Version': project.version)
+        }
+    }
 }
 
 def getVersionForBuild() {