Added ethnologue command (take 2)

[completes this GCI 2013 task](https://google-melange.appspot.com/gci/task/view/google/gci2013/4554769062428672)
Syntax: `.ethnologue <lg>`, where "lg" can be an ISO-639-3 code or partial language name. If there is more than one language for language name given, a "did you mean?" prompt is used instead.
A fix for `.seen` was also attempted.