Reformats some scss for readability

Uses the ampersand parent selector to create a more readable flow in
some files.
Adds %views-row placeholder selector

Reduces some CSS bloat by using a placeholder selector.
Rectifies SUSY layout inconsistencies

Using the last include in wrong contexts are fixed.
Changes off-canvas function

Disables scrolling on narrow layout when off canvas is active, since
sometimes two scrollbars appear for each element.