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/development/libraries/aalib/default.nix

@@ -15,4 +15,8 @@ stdenv.mkDerivation {
 
   buildInputs = [ncurses];
   inherit ncurses;
+
+  meta = {
+    description = "ASCII art graphics library";
+  };
 }