Next IM client: add a few candidate requirements.

wiki/src/blueprint/replace_Pidgin.mdwn

@@ -62,6 +62,15 @@ TODO: Pidgin already has an apparmor profile; should we require that a replaceme
 
 The client MUST NOT save logs of conversations.
 
+### Candidates
+
+Suggested by sajolida on <https://mailman.boum.org/pipermail/tails-dev/2016-January/010123.html>:
+
+* private group chat
+* search and archive past public communications
+* offline-friendliness
+* <https://dymaxion.org/essays/pleasestop.html>
+
 ## XMPP (Jabber)
 
  *( Here is a [list](https://developer.pidgin.im/wiki/SupportedXEPs) of XMPP extensions supported by Pidgin )*