Dehardcode camera

• Lua bindings for camera. See updated example mods (video 1, 2, 3, 4, 5).
• These mods are also an example that several mods can alter camera behavior at the same time without conflicts.
• Dehardcoding is started! This MR removes more C++ code than adds, and moves camera-related logic to Lua.
• It illustrates the approach to built-in scripts, script interfaces, and dehardcoding in general.

Testing is required!
Note that now you always use built-in camera Lua script even if you don't have Lua mods. Please test everything that is related to camera. Without mods the behavior should be exactly the same as before (except a small fix for head bobbing on a very high speed).