Improved use of vk.com API to increase a chance of getting user ID and nickname.

The new version uses vk.com API to retrieve nickname of the user if started on page with vk.com ID-based URL.

Note that not logged in users are not able to use vk.com API, so no nickname may be retrieved this way. However, if the user profile URL is nickname-based, the extension is able to pick it up without using vk.com API at all.