Tone mapper

[Goshido]

It's needed to develop automatic tone mapper into pbr subproject. Tone mapper should mimic autoexposure and human eyes adaptation.

Steps

• [x] Get familiar with implementation #1
• [x] Get familiar with implementation #2
• [x] Select average brightness algorithm
• [x] Understand implementation details of SPD algorithm
• [x] Implement average brightness algorithm
• [x] Select auto-exposure algorithm
• [x] Implement auto-exposure algorithm
• [x] Select tone mapper algorithm
• [x] Implement tone mapper algorithm
• [x] Introduce user brightness setting
• [x] Allow to set tone mapper parameters from script
  • [x] Min brightness in EV
  • [x] Max brightness in EV
  • [x] Exposure compensation in EV
  • [x] Eye adaptation speed
  • [x] Brightness
• [x] Update preview image on main page
• [x] Merge feature to main branch

[Goshido]

AMD SPD average brightness has been implemented. The result has been compared with brute force average brightness using float64. There is a noticeable precision difference.