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/applications/version-management/git-and-tools/git-crypt/default.nix

@@ -21,7 +21,7 @@ stdenv.mkDerivation rec {
 
   meta = with stdenv.lib; {
     homepage = "https://www.agwa.name/projects/git-crypt";
-    description = "transparent file encryption in git";
+    description = "Transparent file encryption in git";
     longDescription = ''
       git-crypt enables transparent encryption and decryption of files in a git
       repository. Files which you choose to protect are encrypted when