assist #11675: do not assume sun.nio.ch.DirectBuffer

need to achieve
	((sun.nio.ch.DirectBuffer) this.data).cleaner().clean();
without breaking if sun.nio.ch.DirectBuffer is not as expected,
see https://github.com/openmicroscopy/openmicroscopy/pull/1865#discussion_r8370560
make config value case-insensitive

suggested by @bpindelski
Merge pull request #1910 from mtbc/trac-11675-leaking-direct-buffers

assist #11675: do not assume sun.nio.ch.DirectBuffer