Revamp document completion %

[EirikBirkeland]

Current "xx% complete" indication is based on number of segments. This is particularly inaccurate for some documents that contain a couple of very long segments.

• Add a % complete view which shows % based on number of words remaining.

Easy:

const totalWords = segmentCollection.map(segment => segment.getRawText()).join(" ").split(" ").length;
const translatedWords = segmentCollection.map(segment => segment.status = "translated").join(" ").split(" ").length;

const percentageCompleted = translatedWords / totalWords * 100;