[refactor] Remove the word 'Manager' from most source files/namespaces

ChatManager -> Chat
MissionManager -> Missions
NanoManager -> Nanos
TransportManager -> Transport
ChunkManager -> Chunking
BuddyManager -> Buddies
GroupManager -> Groups
RacingManager -> Racing
ItemManager -> Items

NPCManager and PlayerManager remain.

Note: You can use git log --follow src/file.cpp to trace the history of
a file from before it was renamed.

src/Chat.hpp

@@ -0,0 +1,13 @@
+#pragma once
+
+#define CMD_PREFIX '/'
+
+#include "CNShardServer.hpp"
+
+namespace Chat {
+    extern std::vector<std::string> dump;
+    void init();
+
+    void sendServerMessage(CNSocket* sock, std::string msg); // uses MOTD
+    std::string sanitizeText(std::string text, bool allowNewlines=false);
+}