Exception handling

[bocops]

Based on discussion in PR #353, we should decide how we want our exception handling to look like. There's a number of points to consider and discuss:

1. Exceptions in Kotlin are generally unchecked, meaning an exception thrown by one function does not need to be caught, rethrown, wrapped or declared by any function direct or indirectly calling the first. This propagates to Java, unless the Kotlin function that throws is explicitly annotated to do so using @Throws. We need to decide, do we want our exceptions to be checked (using the annotation) or unchecked (not using the annotation) in Java?
2. Do we ever want to throw generic exceptions, or do we want to make sure that all exceptions thrown by our code are some variant of BigBone*Exception? For example, some client-side validation throwing IllegalArgumentException currently exists (see Introduce client-side validation on methods #293 and PR referenced there).
3. Would it be useful for all our exceptions to inherit from a BigBoneException superclass? This would allow catching all exceptions thrown by our code at once.
4. Naming: do we want all our exception classes to be named with a "BigBone" prefix, or does it suffice for one or some superclasses to be named like that? Currently, subclasses of BigBoneClientInstantiationException do not use the prefix, which seems sensible because these names are a mouthful after a while.

If a decision has been made

• the Wiki page API support needs to be updated, or removed if we no longer want to keep it.
• documentation on how our exceptions behave, especially in a Java context if we decide to make them unchecked, needs to written.
• issues to update existing code need to be opened as necessary.