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/tools/admin/analog/default.nix

@@ -30,7 +30,7 @@ stdenv.mkDerivation {
   meta = {
     homepage = "http://www.analog.cx/";
     license = "GPL";
-    description = "a powerful tool to generate web server statistics";
+    description = "Powerful tool to generate web server statistics";
     maintainers = [ stdenv.lib.maintainers.simons ];
     platforms = stdenv.lib.platforms.linux;
   };