officeotron is a OOXML documents validator which can be used for
verification of export files in tests. Previously it was possible
to use it only from external repository with extra build steps.

Change-Id: Iae6ec3695fdfaf738d180405047ff04b2024c906
Reviewed-on: https://gerrit.libreoffice.org/27388Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>