Add different error handling behaviors for disk writing errors

[KaiOelfke]

I was using Puppy during debugging a low disk space scenario. One crash was actually a side effect of logging with Puppy. The disk write failed due to low disk space. Using force trying to log is not always the right behavior for each logging use case.

For this scenario it's better to potentially lose some logs than to crash the app.

This PR adds two more error handling strategies for disk writes. There may be other valid error handling strategies.

• assert uses assertionFailure to stop execution for debug builds and ignores failures in release builds
• print only prints the error message to the standard output

The default option force has the current behavior. So this shouldn't be a breaking change, but allows Puppy users to pick a different behavior, when useful.

[sushichop]

@KaiOelfke
This use case is very helpful.
Thanks for your excellent pull request!