Bug 12651: DOM indexing is the default

Bug 12651: DOM indexing is the default

On the 23 July development meeting it was decided to formally deprecate
GRS-1 indexing mode for Zebra. This patch makes code fallback to DOM
on the remaining places. No behaviour change should be noticed, as DOM
has been the default for a while.

Regards

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Passes tests and QA script.
Also checked running Makefile.PL

Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>