This allows to have two cell anchored types:
* Only cell anchored (moves with the cell when sorting etc)
* Cell anchored, also resizes with the cell

Beforehand, all cell anchored images would resize with the cell,
which was often not what users expected.

The new default (when inserting images) is now that inserted images
are only anchored to the cell, but don't resize with the cell.

This makes use of the ODF elements table:end-cell-address, table:end-x, table:end-y.
When images should resize with the cell, the end address is written
(it has always been written earlier, so documents would still import correctly).
If not, they are omitted.

Also implements xlsx import & export

Change-Id: I5f96242f88943ed77a0fd12b7f39b444e1380df7
Reviewed-on: https://gerrit.libreoffice.org/49490Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Samuel Mehrbrodt <Samuel.Mehrbrodt@cib.de>