CLIENT: fix broken observer removal in CommandProcessorComposite

dispose() method wasn't actually running.
MXGDA-343 Move status control creation/layout to new method in CommandProcessorComposite
MXGDA-343 Add new layout that uses groups to CommandProcessorComposite (disabled for now)
MXGDA-343 Make new layout in CommandProcessorComposite dependent on new property

Property is uk.ac.gda.client.CommandProcessorComposite.showgroups
Merge branch 'MXGDA-343'