Update for shift of CharOffsets code to bue-common-open
Bugfix: Multiple consecutive tabs in input were being collapsed.

This caused a cryptic error message if you leave a field blank.
Bump bue-common-dependency to 2.9.0-SNAPHOT
Massive revamp of how coreference is handled.

Coreference IDs are no longer stored (internally) on responses but rather in a separate
coreference object.  This makes it easier for the assessment tool to save coreference information
even for unassessed tuples, which enables a 'coref-then-assess' workflow which will be needed
for the evaluation.