GNOME development group updates in comps

[Bastien Nocera]

Hey,

I've updated the comps file in Fedora 20 to be more useful to application
developers, and bug reporters alike.

This makes "yum install @gnome-software-development" install:
- Command-line utilities like diffstat, valgrind, gdb
- GNOME developer tools like gitg, gtkparasite
- Additional libraries like clutter-gst-devel, polkit-devel
- And devel docs for GStreamer, webkit, glib and clutter

Please take a look over the comps-f20.xml file in:
https://git.fedorahosted.org/cgit/comps.git/

And let us know if, as GNOME/Fedora developers, there's anything else
that ought to be installed by default for budding developers.

Not that this is for application development, not GNOME development itself,
so things like totem-pl-parser, grilo, or gnome-online-accounts' devel packages
are getting dragged in. Those should be pulled by "yum-builddep" instead, when
you hack on a particular package.

Cheers