Support tilt in headless rendering

[maxammann]

🤔 Expected Behavior

Tilting the camera in headless mode should still yield valid tiles.

😯 Current Behavior

Not sure what happens right now.

💁 Possible Solution

We might want to introduce a special camera for headless rendering.

🔦 Context

On FOSS4G I discovered that tilting might be incompatible with headless rendering of PNG files. But actually it should work, we just need to make sure that adjacent tiles still match the other tiles.

💻 Examples

None