Added mouse-selection feature for bookmark list buffer.

Added mouse-selection feature for bookmark list buffer.
(bookmark-bmenu-other-window-with-mouse): New function.
(bookmark-bmenu-mode-map): Bind mouse-2.
(bookmark-bmenu-list, bookmark-insert-location,
bookmark-bmenu-hide-filenames): Put text property on bookmarks.
(bookmark-bmenu-show-filenames): Remove text property from
white spaces generated by `move-to-column'.
(bookmark-bmenu-bookmark): Use `buffer-substring-no-properties'
instead of `buffer-substring'.