Sandboxing prevents access to files in user profile as well as to
contents of the LibreOffice.app unless it is manually triggered by the
user. Even a clicking a link pointing to the files on an automatically
opened file is not enough, the user would have to copy'n'paste the
target.
As a workaround force online help when default browser is Safari and
running on 10.14 or later. (other browsers don't seem to enforce
sandboxing yet and continue to work)

also fix error in the meta tag for the intermediate page (delay and URL
are both part of the content attribute and not separate)

Change-Id: I6cc50ec1b1928c2416fdfef4cf50e2196a8594ae
Reviewed-on: https://gerrit.libreoffice.org/73163Tested-by: Xisco Faulí <xiscofauli@libreoffice.org>
Tested-by: Jenkins
Reviewed-by: Olivier Hallot <olivier.hallot@libreoffice.org>
Reviewed-by: Christian Lohmaier <lohmaier+LibreOffice@googlemail.com>