Bug 41690

CustomProperties supports various put methods - e.g. put(String name, Long value).  Each of these 
calls put(CustomProperty) which calculates a unique id for the property and adds it.

If you want to add a property of a custom type you can't build your own CustomProperty and call put
(CustomProperty) because it is private.

You can call put(name, CustomProperty) but this method doesn't allocate a unique ID.  This means you 
need to do your own id management to ensure you assign unique IDs to every property you add.

In my case I wanted to add a non unicode String property.  Unfortunately put(String name, String value) 
sete the type to unicode, so I had to abandon all the built in simple put() methods and build my own 
CustomProperty objects for all attributes so that I could guarantee the IDs for them were unique.