More description fixes

* Remove package name
* Start with upper case letter
* Remove trailing period

Also reword some descriptions and move some long descriptions to
longDescription.

I'm not touching generated packages.

pkgs/tools/misc/ttmkfdir/default.nix

@@ -26,6 +26,6 @@ stdenv.mkDerivation {
   buildInputs = [freetype fontconfig libunwind libtool flex bison];
 
   meta = {
-    description = "Create fonts.dir for TTF font directory.";
+    description = "Create fonts.dir for TTF font directory";
   };
 }