Replace Chevron Icons

We used a rotated chevron icons in various places to make up for the lack of dedicated 'back', 'previous' and 'next' icons.

!508+ Added 'back', 'previous' and 'next' icons as alias for rotated chevrons.

Check all occurrences of Chevron icon and replace them with 'back' 'previous' or 'next' icon, where appropriate 😄 Please also remove the associated rotating css, as the rotation is now built in.