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/video/simplescreenrecorder/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchurl, alsaLib, ffmpeg, jackaudio, libX11, libXext
+{ stdenv, fetchurl, alsaLib, ffmpeg, jack2, libX11, libXext
 , libXfixes, mesa, pkgconfig, pulseaudio, qt4
 }:
 
@@ -12,7 +12,7 @@ stdenv.mkDerivation rec {
   };
 
   buildInputs = [
-    alsaLib ffmpeg jackaudio libX11 libXext libXfixes mesa pkgconfig
+    alsaLib ffmpeg jack2 libX11 libXext libXfixes mesa pkgconfig
     pulseaudio qt4
   ];