[MINOR] add "description", "node" and show-node"/"show-desc", remove "node-name", v2

This patch implements "description" (proxy and global) and "node" (global)
options, removes "node-name" and adds "show-node" & "show-desc" options
for "stats". It also changes the way the header lines (with proxy name) and
the statistics are displayed, so stats no longer look so clumsy with very
long names.

Instead of "node-name" it is possible to use show-node/show-desc with
an optional parameter that overrides a default node/description.

backend cust-0045
        # report specific values for this customer
        stats show-node Europe
        stats show-desc Master node for Europe, Asia, Africa
diff --git a/include/types/proxy.h b/include/types/proxy.h
index 8c93e55..2cdf689 100644
--- a/include/types/proxy.h
+++ b/include/types/proxy.h
@@ -233,7 +233,7 @@
 		int httpreq;                    /* maximum time for complete HTTP request */
 		int check;                      /* maximum time for complete check */
 	} timeout;
-	char *id;				/* proxy id */
+	char *id, *desc;			/* proxy id (name) and description */
 	struct list pendconns;			/* pending connections with no server assigned yet */
 	int nbpend, nbpend_max;			/* number of pending connections with no server assigned yet */
 	int totpend;				/* total number of pending connections on this instance (for stats) */