BLVIII-24 after testing on beamline

 - this will now add two columns to the data out: vertical and horizontal gradient
EPICS BLVIII-14 (8.40) Created a DummyConstantVelocityRasterScannable Scannable suitable for use in {@link ConstantVelocityRasterScan}s for a dummy controller.
Revert "EPICS - Extend StandardTriggerMode enum"

This reverts commit 6232d68f8ed58d9739e157c0b153518905fed192.
PhaseContrastCalculationPlugin was upgraded with the correct 
calculation of vertical and horizontal gradients.
Merge branch 'gda-8.40' of ssh://dascgitolite@dasc-git.diamond.ac.uk/gda/gda-epics.git into gda-8.40