Captialize meta.description of all packages

In line with the Nixpkgs manual.

A mechanical change, done with this command:

  find pkgs -name "*.nix" | \
      while read f; do \
          sed -e 's/description\s*=\s*"\([a-z]\)/description = "\u\1/' -i "$f"; \
      done

I manually skipped some:

* Descriptions starting with an abbreviation, a user name or package name
* Frequently generated expressions (haskell-packages.nix)

pkgs/development/libraries/libdwg/default.nix

@@ -11,7 +11,7 @@ stdenv.mkDerivation {
   nativeBuildInputs = [ indent ];
 
   meta = {
-    description = "library reading dwg files";
+    description = "Library reading dwg files";
     homepage = http://libdwg.sourceforge.net/en/;
     license = stdenv.lib.licenses.gpl3;
     maintainers = [stdenv.lib.maintainers.marcweber];