Rename sidebar_collapsed and code style

sidebar_collapsed is more consistent with other options and setting names we use. Better change it before the next release rolls out otherwise we'd have to do a version upgrade.
Also changed some code style things to be in line with our guidelines.

Contributes to issue CURA-4234.

cura/CuraApplication.py

@@ -316,7 +316,7 @@ class CuraApplication(QtApplication):
         preferences.addPreference("cura/material_settings", "{}")
 
         preferences.addPreference("view/invert_zoom", False)
-        preferences.addPreference("cura/sidebar_collapse", False)
+        preferences.addPreference("cura/sidebar_collapsed", False)
 
         self._need_to_show_user_agreement = not Preferences.getInstance().getValue("general/accepted_user_agreement")
 

resources/qml/Cura.qml

@@ -401,7 +401,7 @@ UM.MainWindow
                         collapseSidebarAnimation.start();
                     }
                     collapsed = !collapsed;
-                    UM.Preferences.setValue("cura/sidebar_collapse", collapsed);
+                    UM.Preferences.setValue("cura/sidebar_collapsed", collapsed);
                 }
 
                 anchors
@@ -432,9 +432,10 @@ UM.MainWindow
 
                 Component.onCompleted:
                 {
-                    var sidebarCollapsed = UM.Preferences.getValue("cura/sidebar_collapse");
+                    var sidebar_collapsed = UM.Preferences.getValue("cura/sidebar_collapsed");
 
-                    if (sidebarCollapsed) {
+                    if (sidebar_collapsed)
+                    {
                         sidebar.collapsed = true;
                         viewportRect = Qt.rect(0, 0, 1, 1.0)
                         collapseSidebarAnimation.start();

resources/qml/Topbar.qml

@@ -25,9 +25,12 @@ Rectangle
     property int allItemsWidth: 0;
 
     function updateMarginsAndSizes() {
-        if (UM.Preferences.getValue("cura/sidebar_collapse")) {
+        if (UM.Preferences.getValue("cura/sidebar_collapsed"))
+        {
             rightMargin = UM.Theme.getSize("default_margin").width;
-        } else {
+        }
+        else
+        {
             rightMargin = UM.Theme.getSize("sidebar").width + UM.Theme.getSize("default_margin").width;
         }
         allItemsWidth = (