Add a cooperative mode

[Antoine cezar]

I've sucessfully made it work with a dirty hack:

Index: source/network/NetServer.cpp
===================================================================
--- source/network/NetServer.cpp	(révision 14856)
+++ source/network/NetServer.cpp	(copie de travail)
@@ -645,7 +645,7 @@
 	PlayerAssignment assignment;
 	assignment.m_Enabled = true;
 	assignment.m_Name = name;
-	assignment.m_PlayerID = playerID;
+	assignment.m_PlayerID = 1;
 	m_PlayerAssignments[guid] = assignment;
 
 	// Send the new assignments to all currently active players

It worked with a modified host and an unmodified client, but you must not touch to the human player placement.

Since seemed to be just a mater of playerID I thougth that tweaking the gamesetup.js should do the trick. But whatever attempt I've made ended in "nothing happened" or "coredump".

I've spotted a potential reason in CNetServerWorker::AssignPlayer which "Remove anyone who's already assigned to this player" before assigning the new playerID and introduced my own method which just set on gui playerID to the other:

void CNetServerWorker::SetCooperation(const CStr& firstGuid, const CStr& secondGuid)
{
	if (m_PlayerAssignments.find(firstGuid) != m_PlayerAssignments.end()
	&&  m_PlayerAssignments.find(secondGuid) != m_PlayerAssignments.end())
	{
		
		m_PlayerAssignments[secondGuid].m_PlayerID = m_PlayerAssignments[firstGuid].m_PlayerID;
		SendPlayerAssignments();
	}
}

And tweaked gamesetup again, but nothing works for now.