Removed the special hack for 'Refinery Translator' role.

This adds complication to the core for a feature that could easily
be added by an extension when required.
Merge pull request #2730 from refinery/remove-translator-role

Removed the special hack for 'Refinery Translator' role.
Fixed bug: clicking Preview button causes Save button to open in a new browser window when clicked.
Vertical admin tabs

Having admin tabs at the top running horizontally means they have to fit into a finite space. If there are too many, they go into a carousel, which is very inconvenient for navigation, and makes the rightmost tabs invisible to users.

I've put the admin tabs vertically at the left of the admin area. This gives as much vertical space (with scrolling) as needed.

- positioned admin tabs vertically at left
- wrapped admin content in #admin_container div
- corresponding #login_container div for login page
- more rounded corner mixins
- box-sizing mixin
- admin_background mixing provides faux column gradient background for admin area (modern browsers and IE10 up)
- SASS variables for $menu_width and $standard_rounding
- sortable_menu.js setting changed to y axis
- removed jcarousel and images

Conflicts:
	core/app/assets/images/refinery/carousel-left.png
	core/app/assets/images/refinery/carousel-right.png
	core/app/assets/stylesheets/refinery/layout.css.scss
- replaced arrow_switch.png with arrow_up_down.png and arrow_left_right.png
- moved SASS utility mixins to a separate file
- generalised admin_background() mixin to faux_columns_2()

Conflicts:
	core/app/assets/stylesheets/refinery/layout.css.scss
- removed different padding/margin for active tab
- Increased admin width.
- Removed admin rounding.
- Gave menu a defined background.
- Changed width of search box.