Support RTL/BiDi website layout

[jordangriffiths01]

Currently, the html attribute dir is set to RTL when required, which gets us part of the way there. However more changes are needed to truly mirror the layout. This essentially boils down to switching 'left' with 'right' in css rules and html classes in all but a few exceptional cases.

Some good suggestions for how to use sass/scss features to achieve this are included in this blog: http://matanich.com/2013/09/06/rtl-css-with-sass