[Standards-JIG] JEP-0060: sending last published item

[Ian Paterson]

> ...configuration option that enables the node owner to specify 
> when the last published item is sent out. I think we can call 
> this field "pubsub#send_last_published_item" and make it of 
> type "list-single" with the following options:
> 
> 1. never send the last published item
> 
> 2. send the last published item only to new subscribers
> 
> 3. send the last published item to new subscribers and also 
> to newly available resources for existing subscribers

This new option is more complete than the existing
'pubsub#send_item_subscribe' ('Whether to send items to new
subscribers'). So can 'pubsub#send_item_subscribe' be removed now?

- Ian