Use Levensthein distance to approximate correctness of entries for !register and !addroles

[tigressine]

And associated opposite commands.

If we match strings and say that the Levensthein distance can be 0 or 1 then that allows for 1 letter typos.

!register cs1_hensal
!register #cs1_szumlanski

With a 1 character difference tolerance both of these commands would work! Could make distance <= 2 if we were feeling ballsy and no class names are 2 changes apart... Or maybe they'd all have to be 4 changes apart?