Prefix subprojects with 'smack-'

instead of using the old baseName=smack appendix=project.name approach,
we are now going convention over configuration and renaming the
subprojects directories to the proper name.

Having a prefix is actually very helpful, because the resulting
libraries will be named like the subproject. And a core-4.0.0-rc1.jar is
not as explicit about what it actually *is* as a
smack-core-4.0.0-rc1.jar.

SMACK-265

smack-compression-jzlib/build.gradle

@@ -0,0 +1,8 @@
+description = """\
+Compression with jzlib
+Allow to compress the XMPP stream with help of jzlib."""
+
+dependencies {
+	compile project(path: ':smack-core', configuration: 'compression')
+	compile 'com.jcraft:jzlib:1.1.3'
+}