check context menu opening at beginning of callback function

* The context menu state doesn't change once the callback function starts, so
  that we should check the state at the head of the function to avoid the
  following useless processing.
update score format

* has 3 digits after the point and appends zero padding for readability
adopt all scored items

* I think it doesn't increase the scored items so much not to cut off low point
  ones.
fix invalid point for URL comparison
remove unnecessary check of same path URL

* A target URL with the same path as the original URL is filtered out in the
  caller function |SiblingNavi::guessBySearching|.