Randomisations - add option to control group properties

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The randomisations currently do nothing to the group properties, and simply 
re-assign them to the randomised basedata.  

An option needs to be added to control this behaviour.  

The same goes for label properties.


The potential fly in the ointment is that property tables will become first 
class objects.  At that point it is worth overhauling the randomisation 
approach to also work on trees and matrices, handling as many as are used in 
analysis arguments.  

Original issue reported on code.google.com by shawnlaffan on 8 Jul 2013 at 6:25

• Blocked on: Randomisations - cache args at the run_analysis level #391