Some description fixes

There are many more packages to fix, this is just a start.

Rules:
 * Don't repeat the package name (not always that easy...)
 * Start with capital letter
 * Don't end with full stop
 * Don't start with "The ..." or "A ..."

I've also added descriptions to some packages and rewritten others.

pkgs/applications/misc/abook/default.nix

@@ -13,7 +13,7 @@ stdenv.mkDerivation rec {
 
   meta = {
     homepage = "http://abook.sourceforge.net/";
-    description = "Abook is a text-based addressbook program designed to use with mutt mail client.";
+    description = "Text-based addressbook program designed to use with mutt mail client";
     license = "GPLv2";
     maintainers = [ stdenv.lib.maintainers.edwtjo ];
     platforms = with stdenv.lib.platforms; linux;