jack: change package and attr names to 'jack1' and 'jack2'

Currently, we have a 'jack' package with attrname 'jack1d' and a
'jackdbus' package with attrname 'jackaudio'. Make it consistent 'jack1'
and 'jack2' in both package name and attrname.

This aligns the naming with what can be found on the JACK homepage.

Q: what's the difference between jack1 and jack2?
A: http://trac.jackaudio.org/wiki/Q_differenc_jack1_jack2

pkgs/development/interpreters/supercollider/default.nix

@@ -1,5 +1,5 @@
 { stdenv, fetchurl, cmake, pkgconfig
-, jackaudio, libsndfile, fftw, curl
+, jack2, libsndfile, fftw, curl
 , libXt, qt, readline
 , useSCEL ? false, emacs
 }:
@@ -35,6 +35,6 @@ stdenv.mkDerivation rec {
   nativeBuildInputs = [ cmake pkgconfig ];
 
   buildInputs = [ 
-    jackaudio libsndfile fftw curl libXt qt readline ] 
+    jack2 libsndfile fftw curl libXt qt readline ]
     ++ optional useSCEL emacs;
 }