Some description fixes

There are many more packages to fix, this is just a start.

Rules:
 * Don't repeat the package name (not always that easy...)
 * Start with capital letter
 * Don't end with full stop
 * Don't start with "The ..." or "A ..."

I've also added descriptions to some packages and rewritten others.

pkgs/development/misc/avr-gcc-with-avr-libc/default.nix

@@ -79,7 +79,7 @@ stdenv.mkDerivation {
   };
 
   meta = { 
-      description = "avr gcc developement environment including binutils, avr-gcc and avr-libc";
+      description = "AVR developement environment including binutils, avr-gcc and avr-libc";
       # I've tried compiling the packages separately.. too much hassle. This just works. Fine.
       license =  ["GPL" "LGPL"]; # see single packages ..
       homepage = []; # dito