Make an option to allow synonyms to be optional

[jdelange22]

Right now there is an option to mark the translation as partially correct when the synonym is not entered. It would make sense to also add an option that allows either one of the two words (original translation or synomym) to be entered and when entered correctly marks the word as properly translated.

[daniel-lerch]

This could be part of #20 where I wanted to introduce such an option for all the partially correct cases.