Header no longer prevents node hover/click

This introduces an inverse thingy, whenever you add something to the
header you have to be aware that by default you won't get any pointer
events and that you'll have to enable them for the dom elements you
wanna make interactive.

client/app/styles/main.less

@@ -165,6 +165,8 @@ h2 {
 }
 
 .header {
+  pointer-events: none;
+
   position: absolute;
   top: 32px;
   width: 100%;
@@ -264,6 +266,8 @@ h2 {
   .topologies-item-main,
   .topologies-sub-item {
     // border: 1px solid @background-darker-secondary-color;
+    pointer-events: all;
+
     color: @text-secondary-color;
     .btn-opacity;
     cursor: pointer;
@@ -1189,6 +1193,8 @@ h2 {
 }
 
 .grid-mode-selector {
+  pointer-events: all;
+
   margin-top: 8px;
   margin-left: 8px;
 
@@ -1278,6 +1284,8 @@ h2 {
 }
 
 .search {
+  pointer-events: all;
+
   display: inline-block;
   position: relative;
   width: 10em;