Implemented PlugLayout updates triggered by Metadata changes.
Implemented PlugLayout updates triggered by Metadata changes.

Currently this just allows dividers to be added and removed on demand.

johnhaddon/gaffer,johnhaddon/gaffer,appleseedhq/gaffer,ImageEngine/gaffer,johnhaddon/gaffer,GafferHQ/gaffer,hradec/gaffer,GafferHQ/gaffer,boberfly/gaffer,GafferHQ/gaffer,ImageEngine/gaffer,lucienfostier/gaffer,chippey/gaffer,goddardl/gaffer,andrewkaufman/gaffer,ImageEngine/gaffer,hradec/gaffer,davidsminor/gaffer,cedriclaunay/gaffer,davidsminor/gaffer,johnhaddon/gaffer,appleseedhq/gaffer,chippey/gaffer,lucienfostier/gaffer,cedriclaunay/gaffer,appleseedhq/gaffer,lucienfostier/gaffer,andrewkaufman/gaffer,cedriclaunay/gaffer,ivanimanishi/gaffer,ivanimanishi/gaffer,boberfly/gaffer,boberfly/gaffer,chippey/gaffer,andrewkaufman/gaffer,GafferHQ/gaffer,GafferHQ/gaffer,johnhaddon/gaffer,cedriclaunay/gaffer,hradec/gaffer,davidsminor/gaffer,andrewkaufman/gaffer,appleseedhq/gaffer,ImageEngine/gaffer,andrewkaufman/gaffer,goddardl/gaffer,goddardl/gaffer,lucienfostier/gaffer,ivanimanishi/gaffer,hradec/gaffer,boberfly/gaffer,goddardl/gaffer,hradec/gaffer,chippey/gaffer,ivanimanishi/gaffer,davidsminor/gaffer