Adding support for opening EventSource with a pre-known eventId

Hi,

I tried to use a jersey client with an SSE stream in following scenario:

The client subscribes to the stream and persist the current eventId to a database.
After a restart, the client reads the persisted last id from the database and wants to reconnect to the stream with the pointer to the current event. This feature is already supported if the client looses his connection but unfortunately not for restarting the whole client.

If tried to fix the issue by #3600. It would be nice, if you could consider to merge this.