Austin

- Made modifications to GLUT_Plotter and added abstract `Screen::applyLayout()` to support resizing of the window, along with support for dynamically resizing and moving Drawable elements. This means you can anchor something to the edge of the window (minus an offset if you wish), and as long as you properly implemented `YourChild::applyLayout()` and make a call to `applyLayout()` in `YourChild::doBackground()`, stuff will stay anchored and in general "just work". See Game.cpp for example.
- Proper tetromino spawning (Closes #27)
- Tetrominos fall (Closes #26)
- Soft fall
- Pause screen