Make Word Guess properly scorable

[clpetersonucf]

While the "Mad Libs" concept is interesting, it's not especially useful pedagogically, and Word Guess could become a much more significant widget in the catalog if it had an actual scoring mechanism that assessed each entry in the empty spaces of a paragraph. This shouldn't be especially difficult to implement, we'd mostly just have to add some extra UI to the creator to allow instructors to select which option they prefer.

[chrissolanilla]

assigning myself this issue