Revert bookmarks refactor (causes more issues than it fixes),

This reverts commit 6c890a95222228d3773fb6efe1f98f31f1102540.
Fix original unmount crash a different way
Show custom colors and emblems in places sidebar
bookmarks:  Use singleton for bookmark-list, track visited (for icon
updates), distinguish 'opened' network bookmarks from available.
bookmarks: ensure visited state for a newly-added bookmark
recent files: show/hide based on gtk remember-recent-files
setting.
places-sidebar:  Add dedicated bookmarks section.

New behavior:
- New user - xdg folders display under home/desktop, as before
- Upgrading user - all bookmarks are unchanged, still display in current position.
- Adding new bookmarks via menus - new items are placed under a Bookmarks category.
  They can be dragged to the My Computer section if desired.
- Performing any sort of drag operation (either a new drag from outside the sidebar
  or re-arranging bookmarks, will temporarily display the Bookmarks heading, to
  reveal the new section.  If the user ends the drag without dropping anything in this
  new section, the heading disappears again.
- Bookmarks can be dragged around between sections without restriction - the bookmark
  section will only show if there are items within it.
add the ability to show/hide all of the toolbar buttons
Merge pull request #727 from JosephMcc/toolbar1

add the ability to show/hide all of the toolbar buttons
search/recent: add "Open containing folder"
Add nemo-open-with standalone program