correctly dispose to avoid cyclic dependencies

accessibility cruft is still listening to dead tables so crashes in
slidesorting in main panel if moved slide has tables in it after visiting slide
sorter once.

Change-Id: I09f9a73b01fb2ddf059402146acdc7bd823798b9
(cherry picked from commit 0b8e2e5efe20519e8b5563314bac0cbb84a3b967)
disposed but not dtored

just die when you are supposed to, without this endless amounts of accessiblity
cells remain after sorting slides with tables in them

(cherry picked from commit 1c28065d8fe3e9a1394a7ecfc29e95a9639a1012)

Conflicts:
	svx/source/table/accessibletableshape.cxx

Change-Id: Ice9a86b8b806e58f9bf871341a38f7729798dda9