Smooth outer boundary terrain

[Besjan]

• [x] Make it smoother
• [x] Fix direction
• [x] Foreach smooth interations:
  • Foreach terrain point with 0 height:
    • If at least one neighbour point has non 0 height:
      • Get average non 0 height neighbours height
      • Convert average height to meters
      • Smoothed height = height meters - smooth amount
      • Smoothed height percent = smoothed height / terrain size.y
      • Apply smoothed height percent to point
• [x] Foreach terrain 0 height, smooth those closer to boundary using: distance to closest boundary point and a factor (points are not uniform)