Custom UsfmUpdateBlock exception

[Enkidu93]

As we expand the number IUsfmUpdateBlockHandlers it may be helpful to create a custom exception to capture update-block-related information or otherwise include it in the current exceptions if possible (since we've had a practice so far of avoiding creating deeper exception nesting). Or maybe just a UsfmParsingException? I continue to think that moving the exception-throwing deeper one layer might be more helpful for debugging - we may not have the project name, but we could provide verse text, ref, etc. which may be more helpful.