This adds a new function to nsNavBookmarks that determines if a place id is a
"real" bookmark (not a livemark child). It also makes a number of places use
this new function to unify and simplify a number of code paths.
Additionally, it changes how frecency is calculated for bookmarked items. If a
visit is bookmarked (aIsBookmarked is true in CalculateFrecencyInternal), the
visited bookmark bonus is now added for all visits. The visit bonus was also
cut in half for bookmarks so TRANSITION_BOOKMARK will still end up with the same
value (150).
r=dietrich
r=MaK77
