Resolves: tdf#126928 allow link updates in an intermediate linked document

Resolves: tdf#126928 allow link updates in an intermediate linked document

... if link updates are allowed in the current document and that
intermediate document resides in a trusted location.

This works with both, the "Always (from trusted locations)" and
the "On request" settings under Tools -> Options -> Calc ->
General. It can't work with documents residing in a non-trusted
location as there is no way to allow updates on demand for a such
loaded document (hidden via formulas).

Reviewed-on: https://gerrit.libreoffice.org/77588
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Jenkins
(cherry picked from commit 54bf84746a2a9a2e2aaf0df9e429b0cfd538f640)

 Conflicts:
	sc/source/ui/docshell/docsh4.cxx
	sc/source/ui/docshell/externalrefmgr.cxx

Backported. Also includes

    commit 1663b1e8233db6c6d1c2b35639ad984961084009
    CommitDate: Tue Feb 26 21:15:57 2019 +0100

        tdf#120736: For Calc shared documents also check the original document URL

Change-Id: Ie483f7743db7c6d5cf947dc16a9c3660855f3423
Reviewed-on: https://gerrit.libreoffice.org/77613
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>
Gbp-Pq: Name allow-link-updates-in-an-intermediate-linked-document.diff