use flex for the default template

(cherry picked from commit 3775be4ce9)

view/css/default.css

@@ -1,22 +1,37 @@
 main {
-	display: table;
-	table-layout: fixed;
 	position: relative;
-	width: 100%;
-	height: 100vh;
+	min-height: 100vh;
+	display: flex;
+	flex-direction: column;
 }
 
-aside {
+.content {
+	display: flex;
+	flex: 1;
+}
+
+.columns {
+	display: flex;
+	flex:1;
+	min-width: 0;
+}
+
+#region_1 {
 	position: relative;
-	display: table-cell;
-	vertical-align: top;
+	order: 1;
 	padding: 4.5rem 7px 0px 7px;
 }
 
-section {
+#region_2 {
 	position: relative;
-	width: 100%;
-	display: table-cell;
-	vertical-align: top;
+	flex: 1;
+	order: 2;
 	padding: 4.5rem 7px 200px 7px;
+	min-width: 0;
+}
+
+#region_3 {
+	position: relative;
+	order: 3;
+	padding: 4.5rem 7px 0px 7px;
 }