Update /othermetas command

Updated /othermetas, changing DW OU for pure Hackmons since DW is now available via challenge only. Changed Seasonal Ladder to generic name to avoid having to update the command every month. Change Tier Shift name to just "Tier Shift" and link ot its thread, added link to "Other Meta of the Month" which will be valid for each month.
Merge pull request #209 from Joimer/patch-9

Update /othermetas command