Suggested words: push words that cover something unique

[HenryWales]

The title is probably not clear. The issue occurs with the relevance of suggestion when dealing with compound words.

For example imagine you have the word "Greatidea". And you get as suggestions: "great", "Greatman", "Greatbuilding", "Greatriver".

To understand the word, you want "great" and "idea" to show up in the list, but because all the words with "great" share 5 characters instead of 4, they show up instead. So separate checking is required.

"Great" covers already perfectly the beginning of the word. So a word that covers well the remaining part of the word should be preferable, and some formula could give a better approximation than the current naive method.

If given some guidance, I could help getting it done.

[HugoFara]

I haven't worked on the related words feature yet, and I think it could be better. The thing is I had very little time for LWT those past weeks, so I don't when and if I could be able to tackle the issue. If you are motivated, I would be happy to look at a pull request.

As a side note, the related terms is quite a minor feature anyway, so I'm not sure whether it's worth the effort.