SP4: Readme; Cluster

This is not clear what is customized by default in term of clustering (UDP or TCP). Only the last paragrph mentions something about some possible ways to turn on UDP config (as it is turn on by default if I remember correctly - so quite confused).

Moreover, it is not indicate the performance issues with UDP configuration and that should be prohibited in production environment.

So we should more clearly state that UDP is great in order to make some quick development tests but TCP is better for production environement. This should be mentionned at the very beginning.

Finally, the introduction only mentions some "browsing nodes". This is not clear as there is confusion between authoring and publishing nodes for the end-users. So I would keep the bullet points mentionning the type of nodes but I would add a small desceription of each type of node just behind.