Docs: Revive old section about Column Picker

Signed-off-by: Remington Steed <rjs7@calvin.edu>
Docs: Revive/merge content into "Using the Staff Client"

This commit brings in three old sections and merges with any similar
content.

- Revive old section about sticky check box settings
- Merge old section about Font and Sound settings

  Adds a brief section about zooming in the OPAC, and otherwise only
  reformats some lines to make them git-friendly.

- Docs: Fix and copy Customize Toolbars section

  The old "Customizable Toolbar" docs section is already revived in the
  Evergreen Book "System Configuration and Customization" chapter. Since
  this feature seems to belong under "Using the Staff Client ->
  Workstation Administration", this commit duplicates it into that
  chapter. This also fixes a few asciidoc bugs in both places.

  In addition, the section "Button Bar/Toolbar" that was also under
  "Workstation Administration" has been moved up a level, since it
  pertains more to staff client users rather than admins. And the
  admin-specific content at the end of that section has been replaced
  with a link to the newly duplicated "Customizable Toolbar" section.

  The result of this reorganization should be:

  - Using the Staff Client
    - Button Bar/Toolbar (for staff client users)
    - Workstation Administration
      - Customizable Toolbar (for staff client admins)

Signed-off-by: Remington Steed <rjs7@calvin.edu>

Conflicts:
	docs/root.txt