DNS-SD/DNSExt gateway service announcement

[thiell]

Instead of having a static topology configuration file on the management node, add a way to use DNS-SD/DNSExt to know about gateway state changes (and maybe load).

[mdenou]

The main research part is done and a PoC is written but it's not Clustershell centric.
For now I am working on performance improvement.

The questions are:
_Should we interface my solution with CS ? If so, how ?
_Or maybe we could integrate my PoC as a full part of CS ?

Third alternative: I make my own side project and we use the concept for a CS functionality.

[degremont]

Could we remove the 3.0 milestone tag for this? Let's see when we will integrate (or not) this feature when ready?