Added /rsset options ( implementing #11 )

[FEATURE] now /rsset has three new options: addeepair [store], deleepair [store] [index] and listeepairs [store] [page]. the index in deleepair command is the one we see when we call listeepairs. I can add a new option where we can delete an EEpair using rsset entrance/exit as we do with rsset addpair. see #11

[CODE] Fixed code duplication in Shop.prices()