use CBanEntry as object container for banned nodes

- added a reason enum for a ban
- added creation time for a ban

Using CBanEntry as container will keep banlist.dat extenable.

src/main.cpp

@@ -4959,7 +4959,7 @@ bool SendMessages(CNode* pto, bool fSendTrickle)
                     LogPrintf("Warning: not banning local peer %s!\n", pto->addr.ToString());
                 else
                 {
-                    CNode::Ban(pto->addr);
+                    CNode::Ban(pto->addr, BanReasonNodeMisbehaving);
                 }
             }
             state.fShouldBan = false;