Last Value Cache Feature for a topic.

Add the Last Value Cache Feature for a topic.
When you will connect to a topic, the last message sent on the topic will be resent to the new client.

For instance, in the bank, without this feature, this JMS is generally not easily useable.
The common case is you want to publish price (bid/ask) on a stock. You have a topic by stock.
When a new client will connect to the topic, he will not receive a message until the price will move.
#### Affected Versions
[2.0]

The issue names no files, tests, or entry points. Start by locating the topic connection and message-delivery implementation, then clarify how the last value is stored, configured, and resent; done means a newly connected client receives the topic's latest message without waiting for another publication.

Written by the indexing model from the issue text.