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/audio/abcde/default.nix

@@ -62,7 +62,7 @@ in
     meta = {
       homepage = "http://lly.org/~rcw/abcde/page/";
       license = "GPLv2+";
-      description = "A Better CD Encoder (ABCDE)";
+      description = "Command-line audio CD ripper";
 
       longDescription = ''
         abcde is a front-end command-line utility (actually, a shell