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/tm/default.nix

@@ -19,7 +19,7 @@ stdenv.mkDerivation {
 
   meta = with stdenv.lib; {
     homepage = "http://vicerveza.homeunix.net/~viric/soft/tm";
-    description = "terminal mixer - multiplexer for the i/o of terminal applications";
+    description = "Terminal mixer - multiplexer for the i/o of terminal applications";
     license = licenses.gpl2;
     maintainers = with maintainers; [ viric ];
     platforms = platforms.all;