Previously pictures could only be synced to grid north, which
can be totally wrong for many CRSes (especially in polar areas)
Users now are given a choice of grid or true north, and can also
enter an optional offset to apply if eg magnetic north is instead
desired.
When synced to true north the bearing is calculated using the
centre point of the linked map item.
Fix#192, #4711
This fix was sponsored by the Norwegian Polar Institute's
Quantarctica project (http://quantarctica.npolar.no) and
coordinated by Faunalia.
