Eliminate samskivert dependency in core.

I've long wanted to do this, but the launcher's use of all the samskivert UI
stuff made it onerous. Now that the launcher is a separate module, we can
remove the samskivert dependency in core (and tools), which simplifies things
and makes it easier to depend on core in a (future) self-updating app (when we
add support for that).

tools/src/main/java/com/threerings/getdown/tools/Differ.java

@@ -21,11 +21,11 @@ import java.util.zip.ZipEntry;
 
 import java.security.MessageDigest;
 
-import com.samskivert.io.StreamUtil;
 import com.threerings.getdown.data.Application;
 import com.threerings.getdown.data.Digest;
 import com.threerings.getdown.data.Resource;
 import com.threerings.getdown.util.FileUtil;
+import com.threerings.getdown.util.StreamUtil;
 
 /**
  * Generates patch files between two particular revisions of an

tools/src/main/java/com/threerings/getdown/tools/Patcher.java

@@ -15,10 +15,9 @@ import java.util.jar.JarEntry;
 import java.util.jar.JarFile;
 import java.util.zip.ZipEntry;
 
-import com.samskivert.io.StreamUtil;
-
 import com.threerings.getdown.util.FileUtil;
 import com.threerings.getdown.util.ProgressObserver;
+import com.threerings.getdown.util.StreamUtil;
 
 import static com.threerings.getdown.Log.log;