Improved cinematic capabilities

[MatthewsSam]

STK should have some improved cinematic capabilities to record easily video, trailer and doing cutscene.

• Possibility to animate a camera during a race + something like look at this kart
• Possibility to have camera rig (like rotating a crane instead of trying to do complex animation on the camera)
• It's easy to have a gimbal lock. This could be difficult since we need to export in quaternion
• Easier cinematic management (currently to do a cutscene the only possibility is to replace one of the stk cutscene by our track)
• Unified behavior with the LoD. The LoD should always use the camera position
• Add a way of easily switching between two camera

[MatthewsSam]

some clarification I don't expect everything for 0.9.1.

[Half-Shot]

So would the first step be having some sort of replay system?

[auriamg]

"Add a way of easily switching between two camera" is now possible using keyboard shortcuts

"Unified behavior with the LoD. The LoD should always use the camera position" is also now the case

[auriamg]

Also see #2482 for the part about launching cutscenes