Add common folder, add grid component, remove home placeholder

* New `common/` folder for `_variables` and `_global`
* Move grid styles to new `_grid` component
* Remove `layouts/pages/_home`

assets/styles/common/_variables.less

@@ -0,0 +1,17 @@
+// Grid settings
+// -------------------------
+
+@main-sm-columns:       @grid-columns;
+@sidebar-sm-columns:    4;
+
+
+// Brand colors
+// -------------------------
+
+@brand-primary:         #27ae60;
+
+
+// Glyphicons path
+// -------------------------
+
+@icon-font-path:        "../fonts/";