Rename CounterLegacy to CounteruGUI

[stilnat]

Hello there, that's a very cool toolkit you did, I'm thinking about using it for my game.
One issue I had is that I really don't want to use the Unity toolkit and for a while I thought there was no samples using it so I almost gave up. CounterLegacy makes you think its some old code that is there just for the sake of keeping it so I did not even bother opening it at first. I think it'd be better named as CounteruGUI to make it clear it's a sample of using uGUI instead of the Unity toolkit.