Option to handle errors gracefully instead of aborting

[bertfrees]

It is a wish of some users to be able to get an output from a (valid) OBFL document regardless of whether there were issues during the conversion. If possible, a valid PEF should be returned, even if it's not the "correct" result, and another return value should indicate whether the PEF is "correct" or not.

It's important to make a distinction between unexpected errors (due to bugs in Dotify), validation errors and other errors. The new option would only have an effect on the last category.

Examples:

• Not enough space in left or right page margin to render content
• Not enough space in header or footer to render content
• Not enough space to render a table with a lot of columns

(A lot more examples can be thought of. We should probably go through the whole code and categorize all the exceptions that are thrown.)

Some errors will be harder to handle gracefully than other. We don't need to handle them all but we should do a best effort.

[bertfrees]

We agreed that it is a good thing in general to try to do a best effort when something can not be rendered according to the OBFL contract, but also provide the option to not deviate from the contract (abort if needed).

However how to best handle it is to be decided case by case.

• In some cases there might be a reasonable fallback that could be always be applied, without the need for a setting. We might have to clarify the new behavior in the OBFL spec.
• In some cases it could make sense to give the use control through a new OBFL feature, like an attribute to enable or disable a fallback.
• In some cases it could be more appropriate to have a Dotify setting.
• Sometimes it might make sense to have a combination.

[bertfrees]

Note that there is already a allowsTextOverflowTrimming option in FormatterConfiguration which could be reused.