CGE2: Some refactoring and fixing regarding runCommand().
CGE2: Partially implement Sprite::step().
CGE2: Revise CGE2Engine::tick().
CGE2: Add isHero().
CGE2: Implement snRSeq() and snSeq().
CGE2: Implement snSound().

Rework the whole Fx class during the process.
The intro animation is working now.