DOC: mention management.txt in README

and in intro.txt as well. Remove references to haproxy-{en,fr}.txt.

README

@@ -424,9 +424,9 @@ There is some documentation in the doc/ directory :
 
            http://cbonte.github.io/haproxy-dconv/configuration-1.5.html
 
-    - haproxy-en.txt / haproxy-fr.txt : these are the old outdated docs. You
-      should never need them. If you do, then please report what you didn't
-      find in the other ones.
+    - management.txt : it explains how to start haproxy, how to manage it at
+      runtime, how to manage it on multiple nodes, how to proceed with seamless
+      upgrades.
 
     - gpl.txt / lgpl.txt : the copy of the licenses covering the software. See
       the 'LICENSE' file at the top for more information.

doc/intro.txt

@@ -78,6 +78,10 @@ to the mailing list whose responses are present in these documents.
     ensure you're running with all known fixes how to update it, complements and
     alternatives.
 
+  - management.txt : it explains how to start haproxy, how to manage it at
+    runtime, how to manage it on multiple nodes, how to proceed with seamless
+    upgrades.
+
   - configuration.txt : the reference manual details all configuration keywords
     and their options. It is used when a configuration change is needed.