Remove the show property from the tooltip

This was a bit of a weird setup, so i removed it. This way the tooltip can be used
in the same way as the regular tooltip (by simply setting the visibility)

CURA-6004

resources/qml/ActionButton.qml

@@ -115,6 +115,6 @@ Button
     Cura.ToolTip
     {
         id: tooltip
-        show: button.hovered
+        visible: button.hovered
     }
 }

resources/qml/ToolTip.qml

@@ -9,29 +9,26 @@ import Cura 1.0 as Cura
 
 ToolTip
 {
-
     enum ContentAlignment
     {
         AlignLeft,
         AlignRight
     }
 
-    // This property indicates when the tooltip has to show, for instance when a button is hovered
-    property bool show: false
-
     // Defines the alignment of the content, by default to the left
     property int contentAlignment: Cura.ToolTip.ContentAlignment.AlignRight
 
     property alias tooltipText: tooltip.text
     property var targetPoint: Qt.point(parent.x, y + Math.round(height/2))
 
-
     id: tooltip
     text: ""
     delay: 500
-    visible: text != "" && show
     font: UM.Theme.getFont("default")
     
+    // If the text is not set, just set the height to 0 to prevent it from showing
+    height: text != "" ? label.contentHeight + 2 * UM.Theme.getSize("thin_margin").width: 0
+
     x:
     {
         if (contentAlignment == Cura.ToolTip.ContentAlignment.AlignLeft)
@@ -43,7 +40,7 @@ ToolTip
 
     y: Math.round(parent.height / 2 - label.height / 2 ) - padding
 
-    padding: 2
+    padding: UM.Theme.getSize("thin_margin").width
 
     background: UM.PointingRectangle
     {

resources/qml/ToolbarButton.qml

@@ -101,6 +101,6 @@ Button
     {
         id: tooltip
         tooltipText: base.text
-        show: base.hovered
+        visible: base.hovered
     }
 }