Fix for ClassCastException in eventuallyEmptyList, where SdtCell contains another SdtCell
Manually applied Tinne's https://github.com/tinne/docx4j/commit/fde4065d5ac33d01072c8659ead88fa165d56477
(which was against VERSION_2_8_1)
Manually applied Tinne's https://github.com/plutext/docx4j/pull/65; eclipse m2e plugin setting: add additional source directories on
incremental builds as well.