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/applications/audio/a2jmidid/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchurl, alsaLib, dbus, jackaudio, pkgconfig, python }:
+{ stdenv, fetchurl, alsaLib, dbus, jack2, pkgconfig, python }:
 
 stdenv.mkDerivation rec {
   name = "a2jmidid-${version}";
@@ -9,7 +9,7 @@ stdenv.mkDerivation rec {
     sha256 = "0pzm0qk5ilqhwz74pydg1jwrds27vm47185dakdrxidb5bv3b5ia";
   };
 
-  buildInputs = [ alsaLib dbus jackaudio pkgconfig python ];
+  buildInputs = [ alsaLib dbus jack2 pkgconfig python ];
 
   configurePhase = "python waf configure --prefix=$out";