handle address query as search if it contains space

[sleep-walker]

When the entered address contains space, we can be rather certain that the content is not URL but webjump.

Let's add option which automatically use default webjump to handle the query.

1. I'm aware that the naming is not stellar.
2. I was considering more options how to get the same functionality but I'd need to duplicate WebJumpPrompt.value in some inherited class and monkey-patch wj_prompt()

[sleep-walker]

OK, it's still not working as expected with the bookmarks containing space. Not for merge yet.