Nodelist Returns: this commits refurbishes the nodelist implementation:
	- the code was refurbished
	- useless functions (nodelist folding) were removed
	- the nodelist now follows a "map" logic

Now a string like "cluster[10-20,34,36,40-50].c-clustre" won't be extended
into a long, comma separated, list. Each item (let's say "cluster43.c-cluster"
in my examples) will be passed as argument to a callback passed as argument.

Usage : pass to the nodelist_map_condensed() function a callback which add the
nodes into the client list.