CtdlGetSysConfig() and CtdlPutSysConfig() now have the ability to store large configu...

CtdlGetSysConfig() and CtdlPutSysConfig() now have the ability to store large configuration items as message texts in the Local System Configuration room by saving their message numbers as items in the regular configuration database.  This eliminates the last place where we did 'Delete all other messages in this room which have the same MIME type' and that ability has therefore been removed from the code.  There is enough code remaining to read configurations saved the old way, but they are upgraded the first time they are read.