Remove column class dependency from component

Remove the need for the global column classes for the component to work.
This will let us use the component outside of the new static template.
It will also enable the component to have finer control over how it is
displayed.
Make document footer component handle rtl content

For RTL content change the text direction and swap the floats so the
reading edge is the other side of the page. There will be a future bit
of work for adding translations to the strings in the component.
Merge pull request #501 from alphagov/rtl-document-footer

Make document footer component handle rtl content