Added GCC warning options and fixed source code according to `-Weffc++`. Also excluded SFML include directory from the checks.

Signed-off-by: Florian Wolters <wolters.fl@gmail.com>
Added "const correctness".
Implemented paddle and ball collision.
Added whitespace before `while`.
Removed duplicate `#include`.
Introduced `Brick` class.
Finished implementing actual game logic.
Enhanced CMake and NetBeans IDE integration and added GTest/GMock.
Initial commit.