Added option on Custom Games List to hide uninstalled games...

Added checkbox to Custom Games list to hide games that the user does not have installed, taking the {Unknown Game} out of the list. 

So now instead of seeing all the games you don't have installed, you can see just the games you can play.  When the checkbox is toggled, it refreshes the list immediately.  As the system grows, should cut down on clutter.

Default is checked.  I cannot see that anyone would ever want it always unchecked, but that could always be a user option.

![image](https://f.cloud.github.com/assets/814669/666714/dbc6b082-d7d2-11e2-841e-20dfc7f7110b.png)

![image](https://f.cloud.github.com/assets/814669/666715/e7858100-d7d2-11e2-9e2e-5eb861cf8c43.png)