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/system/safecopy/default.nix

@@ -9,7 +9,7 @@ stdenv.mkDerivation rec {
   };
 
   meta = {
-    description = "data recovery tool for damaged hardware";
+    description = "Data recovery tool for damaged hardware";
 
     longDescription =
       '' Safecopy is a data recovery tool which tries to extract as much data as possible from a