Adds G75VW to nvidiabl-laptops.h, adds "get" command for nvidiablctl

Thanks for making this module!  It worked for me.  This is my first pull request.

First, it adds the ASUS G75VW gaming laptop to the list in nvidiabl-laptops.h.  That line is based on the hardware info for my laptop which you can see here:
https://gist.github.com/4301964

Secondly, I added a minor feature to nvidiablctl, which is "get" command for getting the brightness.  As soon as I got brightness control working, I wanted the "get" command so I can see the details of what is happening.

Third, I fixed a minor typo in an error message in nvidiablctl.

Finally, I have a question: The nvdiablctl script works great for me, but my backlight function keys do not work.  I have an AUS G75VW-DH72.  Both function keys produce the same output in acpi_listen; both produce the following line:

 PNP0C14:00 000000ff 00000000

Since they both produce the same output, I don't think I can use acpi events to get the hotkeys working.  I was able to get the hotkeys working by using the propritary nvidia driver and setting the appropriate options, but I would like the backlight hotkeys to work under nouveau.  Any advice on that?  What is the basic block diagram for how the backlight hotkeys are supposed to work?  Thanks!