[WIP] Pong example game

[DrDub]

Hello,

I'm learning Magnum and trying mosra/magnum#102

• Simple 2D game (Pong) -- texture loading, input handling, movement calculation, simple animations

This is a base code that shows three triangles and can be played with the keyboard. The "ball" bounces and the computer follows the ball with its paddle.

I'd appreciate some guidance on what you had in mind here w.r.t. to

• texture loading (what textures do you want on a pong game?)
• movement calculations (I'm calculating the movements using Vector2, is there some other functionality from Magnum you want to see here?)
• simple animations (where would you want to see the animation? what type of animation? where in Magnum should I look for the animation functionality?)

This is supposed to be a "simple" example but it starts to cover more and more ground. It currently does not include showing the scores but that'll in a way subsume the 'text' example.

Finally, any guidance in how to get the VertexColorGL2D to make a rectangle rather than a triangle will be appreciated Ball.cpp#56.

[And please comment on the code, I'll be happy to rewrite it in a different direction.]