fix std.EitherEqual
fix EitherRightEqual, EitherLeftEqual
remove unused multiplication objects

These can not be access and there are already alternative tagged typed objects
Merge pull request #537 from xuwei-k/fix-std-either-equal

fix std.EitherEqual
Merge pull request #538 from xuwei-k/either-right-left-equal

fix EitherRightEqual, EitherLeftEqual
fix comments