Rename smack-java7 to smack-java8

Fixes SMACK-854.

smack-java8/build.gradle

@@ -0,0 +1,16 @@
+description = """\
+Smack for Java7 (or higher).
+This is a pseudo-artifact that pulls all the required dependencies to
+run Smack on Java 7 (or higher) JVMs. Usually you want to add additional
+dependencies to smack-tcp, smack-extensions and smack-experimental."""
+
+dependencies {
+	compile project(":smack-core")
+	compile project(":smack-resolver-javax")
+	compile project(":smack-sasl-javax")
+	implementation project(":smack-xmlparser-stax")
+}
+
+javadoc {
+	enabled = false
+}