UP-4305 : Add parameter target so we can have specific portlets launc...

...h in a new window (or target window)


This addition looks suspicious.  It's not clear by looking at this PR or even at the full RDBMDistributedLayoutStore.java file what role this method plays or even how the @Override annotation could possibly compile.  "RDBMDistributedLayoutStore extends RDBMUserLayoutStore" -- my guess is that RDBMUserLayoutStore implements some surprising interfaces... something in the IPortletDefinition tree?  That's not on you, @timlevett (hell... it could easily be on me), but what would it take to clean that up?