Add validation to SuperDataObj instantiation for trailing whitespace in dispname

[bskinn]

This probably wouldn't be that hard -- would just involve changing the validation in SuperDataObj?

Wouldn't be able to use the attrs validators anymore, probably... checking type, no whitespace in all but dispname, plus numerical value only for priority... (no longer constraining priority to numerical values, so no validation here).

Somewhat related to #57.

[bskinn]

Superseded by #152.

Further, trailing whitespace is probably not a major problem, actually, and there's a chance that someone may want to have some there, at some point.