Rename grid-sizes system partial to grid-unit (to not conflict with the newly created grid-sizes component).
Break grid-sizes component into grid, grid-sizes and offset-sizes component partials, for better overview and maintainability.
Rename dimensions utility partial to size.
Singular instead of plural.
(Re)add grid-span system partial (used in size utility partial).
Add additional grid class for percentage gutters, e.g. `Grid--withGutterPercentage`.