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/tools/misc/aescrypt/default.nix

@@ -24,7 +24,7 @@ stdenv.mkDerivation rec {
   NIX_LDFLAGS = stdenv.lib.optionalString stdenv.isDarwin "-liconv";
 
   meta = with stdenv.lib; {
-    description = "encrypt files with Advanced Encryption Standard (AES)";
+    description = "Encrypt files with Advanced Encryption Standard (AES)";
     homepage    = http://www.aescrypt.com/;
     license     = licenses.gpl2;
     maintainers = with maintainers; [ lovek323 qknight ];