Fix for issue 2112.

A new global property has been added to be able to specify to use a ClassLoader 
that limits the search of the bundles to the jar containint the Messages class i
f we are running WebStart setup/upgrader.  This property is only set in the quic
ksetup.properties file, so the current behavior is preserved for all the other m
essages files.  The MessageDescriptor constructors have also been modified and n
ow require a ClassLoader as parameter.  With this modifications we have a ClassL
oader defined in QuickSetupMessages.java that will only be used if we are runnin
g QuickSetup.  The JnlpProperties have been moved to SetupUtils so that the mess
ages classes only depend on classes on the org.opends.server classes that can be
 compiled independently.