Support global and per-user, month+day based logos

Now you just need to create ```mmdd``` folders in ```data/logos``` and then any logos in those directories will show up on that date.  

# Validation
 - [ ] Load ```msfconsole``` as usual.  See some logo.
 - [ ] Set the date to halloween (```sudo date 10310000```).  Start ```msfconsole```. See a halloween logo.