- [sass] better comments formatting
- [nj][sass] layout-related classes now should be prefixed with `l-`; better comments formatting

Prefix needed to avoid possible naming collision between componentes, partials and layout-related classes
- [nj][sass] `.site-menu` classes renamed to `.site-nav`; active states now should be prefixed with `is-`, like `site-nav__item--is-active`

`is-` prefix marks classes that in same time controlled via JavaScript, and on contrary to `js-` prefixed classes _styled_ in CSS
- [sass] `.site-content__heading` reneamed to independant `.site-content-title`; `.site-content-menu-header` changed to `.site-content-nav-title`; better comments formatting
- [sass][grunt] removed unnecessary newline from `sprites.map` template
- [sass] all new shiny ekzo.sass 2.0.0-alpha settings instead of old ones #note All colors still old
- [submodule][ekzo.sass] updated to latest 2.0.0-alpha version