Import of bookmark-folder-search code and tests.
Strip top-level chrome folders.
Require bookmark folder separator to be first character of a query term.
Just ignore known and enumerated top-level folders.
Document top-level folders.
Merge pull request #1063 from fent/master

get new element position for each scroll tested element
Merge pull request #1062 from smblott-github/bookmark-folders

Bookmark search by folder
Adding in search engines feature to fix #1009
Merge pull request #1058 from mijoharas/custom_search_engines

Custom search engines
Improve the help for saved searches
jump forward/backward in scroll jump history
update history positions if they are changed while jumping