new commands to add modeinfo and artist info to maps

mapartist print|set|get|clear

  print:  prints the map artist player ID
  set:  sets the map artist player ID to the currently logged in player
  get:   returns the current map artist player ID
  clear:  erases an existing map artist record in the current map

modeinfo list|get|clear|<modelist> <modeflags>

  list:  lists current modeinfo entries
  get:  returns list of current modeinfo entries
  clear:  erases current list of modeinfo entries
  <modelist> <modeflags>:  specifies flags for a list of modes

DOCREF modeinfo mapartist

source/src/server.h

@@ -454,6 +454,8 @@ void sendf(int cn, int chan, const char *format, ...);
 
 extern bool isdedicated;
 
+const char *modeinfologfilename = NULL;
+
 const char *messagenames[SV_NUM] =
 {
     "SV_SERVINFO", "SV_SERVINFO_RESPONSE", "SV_SERVINFO_CONTD", "SV_WELCOME", "SV_INITCLIENT", "SV_POS", "SV_POSC", "SV_POSN",