Simplify the viewOrientation controls

resources/qml/ViewOrientationButton.qml

@@ -0,0 +1,16 @@
+// Copyright (c) 2018 Ultimaker B.V.
+// Cura is released under the terms of the LGPLv3 or higher.
+
+import QtQuick 2.2
+
+import UM 1.4 as UM
+
+UM.SimpleButton
+{
+    width: UM.Theme.getSize("small_button").width
+    height: UM.Theme.getSize("small_button").height
+    hoverBackgroundColor: UM.Theme.getColor("small_button_hover")
+    hoverColor: UM.Theme.getColor("small_button_text_hover")
+    color: UM.Theme.getColor("small_button_text")
+    iconMargin: 0.5 * UM.Theme.getSize("wide_lining").width
+}

resources/qml/ViewOrientationControls.qml

@@ -7,7 +7,7 @@ import QtQuick.Controls.Styles 1.1
 
 import UM 1.4 as UM
 
-// View orientation Item
+// A row of buttons that control the view direction
 Row
 {
     id: viewOrientationControl
@@ -16,43 +16,33 @@ Row
     height: childrenRect.height
     width: childrenRect.width
 
-    // #1 3d view
-    Button
+    ViewOrientationButton
     {
         iconSource: UM.Theme.getIcon("view_3d")
-        style: UM.Theme.styles.small_tool_button
-        onClicked:UM.Controller.rotateView("3d", 0)
+        onClicked: UM.Controller.rotateView("3d", 0)
     }
 
-    // #2 Front view
-    Button
+    ViewOrientationButton
     {
         iconSource: UM.Theme.getIcon("view_front")
-        style: UM.Theme.styles.small_tool_button
         onClicked: UM.Controller.rotateView("home", 0)
     }
 
-    // #3 Top view
-    Button
+    ViewOrientationButton
     {
         iconSource: UM.Theme.getIcon("view_top")
-        style: UM.Theme.styles.small_tool_button
         onClicked: UM.Controller.rotateView("y", 90)
     }
 
-    // #4 Left view
-    Button
+    ViewOrientationButton
     {
         iconSource: UM.Theme.getIcon("view_left")
-        style: UM.Theme.styles.small_tool_button
         onClicked: UM.Controller.rotateView("x", 90)
     }
 
-    // #5 Right view
-    Button
+    ViewOrientationButton
     {
         iconSource: UM.Theme.getIcon("view_right")
-        style: UM.Theme.styles.small_tool_button
         onClicked: UM.Controller.rotateView("x", -90)
     }
 }