MT-GDA (8.36) Add option to suppress "Path does not exist on IOC" errors.

Several of the Area Detectors on MT beamlines incorrectly report that a
path does not exist when it does so in order to use these area detectors
these errors must be suppressed.
Merge branch '8.36' of ssh://dascgitolite@dasc-git.diamond.ac.uk/gda/gda-epics.git into 8.36
ARPES is using PerimeterROI (extending from Rectangular ones)

Why the list type is different I don't understand.
To keep things simple I do like access to the scisoft
objects, hence making the private method public.

ARPES-224
Merge branch '8.36' of ssh://dasc-git.diamond.ac.uk/gda/gda-epics into 8.36
MT-GDA (8.36) Fix error introduced in 38ed0a0.
Merge branch '8.36' of ssh://dascgitolite@dasc-git.diamond.ac.uk/gda/gda-epics.git into 8.36