FindMissingTypes: New option to check references in Javadoc

[knutwannheden]

Up until now references in Javadoc have always been checked and reported by this recipe. Now this check is optional.

[okundzich]

Curious why we change the default in this recipe (according to the title of this PR) rather than just using a different configuration from the compilation verification

[knutwannheden]

Curious why we change the default in this recipe (according to the title of this PR) rather than just using a different configuration from the compilation verification

I was also unsure about this. Maybe we should indeed keep the default. At the moment we basically just have two uses: The test harness and the compile verification. For the test harness the default is still to check for missing types in Javadoc.

But I can definitely also change the default of the recipe to true.

[knutwannheden]

I lean towards leaving the default as is (not check documentation) because we typically use this recipe to check if something went wrong during the ingestion and missing types in Javadoc are not helpful then, because we can't easily tell if it is the Javadoc that is wrong or not.