[CSS] fix graph height and ergo in folder view

dist/styles/sass.css

@@ -152,10 +152,10 @@
   padding-left: 0.8rem;
 }
 .graph-container .graph-row {
-  height: 100%;
+  height: 100vh;
 }
 .graph-container .graph-row #graph-view {
-  height: 95%;
+  height: 95vh;
 }
 .graph-container #tree {
   position: absolute;

src/Gargantext/Components/FolderView.purs

@@ -108,7 +108,7 @@ backButton =
     className: "btn btn-primary"
   , on: {click: back}
   } [
-    H.i { className: "fa fa-arrow-left"} []
+    H.i { className: "fa fa-arrow-right"} []
   ]
 
 loadFolders :: Record Props -> Aff FTree

src/sass/_graph.sass

@@ -68,10 +68,10 @@
       padding-left: 0.8rem
 
   .graph-row
-    height: 100%
+    height: 100vh
 
     #graph-view
-      height: 95%
+      height: 95vh
 
   #tree
     position: absolute