Objetive Fixes (HONK!)

>Base Type and Unique objectives are no longer added
>Last item in the loot list was not checked. The loot while loop's condition was i<len, but since byond lists start from 1, this would skip the final item in the list (byond is a very weird language)
>Fixed all variants of cosplay aside from the random one appearing
>Tweak antag_types on a bunch of objectives based on community feedback.

Fixes #98
for the record I don't think difficulty actually does anything yet