Update file headers in modules.
Bugfix: Allow $zen-float-direction to affect display of numbers in zen-grid-background() mixin.
Use unquoted strings for $context values in zen-grid-container() mixin.
Change zen-clear's $float-direction paramter to $direction.
Convert $zen-column-count to $zen-columns.
Convert $zen-gutter-width to $zen-gutters.
Convert $zen-float-direction to $zen-direction.

Also, convert $float-direction and $flow-direction parameters to be $direction.
Convert $zen-reverse-all-floats to $zen-switch-direction.

Also, convert $reverse-all-floats and $reverse-all-flows parameters to be $switch-direction.
Rename zen-direction-flip() function to be zen-direction-switch().
Rename zen-clear() mixin to be zen-new-row().
Rename $zen-auto-include-item-base to $zen-auto-include-grid-item-base.

Also, convert $auto-include-item-base parameters to be $auto-include-grid-item-base.