Adding some sentences and words to the Norwegian (nb) translation, and formatting.

Adding the missing phrases `Like`, and `title_by_author `.
Also changing `comment_on_twitter` from "Kommenter" to "Kommentér", because the accent is needed to indicate an action. Norwegian is strange.

A comment => En kommentar
To comment => Å kommentere
comment! => Kommentér!

Funny, eh?