SVY-6615 add server side api support

make flagPropertyChange public, so that the outside world can flag a
property as changed if it is a complex/custom property and the object is
changed internally
SVY-6615 add server side api support

return the property description of the custom type in getProperty(name)
(this property description is the custom type)
SVY-6615 add server side api support

support for serverScript, this should be refactored, pushed outside of
sablo, or sablo can have some support and clients just need to
interpreted that their way?