improve multiselect behaviour for checkboxmodel

when using the mode 'MULTI' for the checkbox selection model,
clicking a row would deselect all others, only clicking exactly on the
checkbox would select multiple rows

this override makes the whole cell of the checkbox behave like the
checkbox. This minimizes misclicks from the user.

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>

src/Toolkit.js

@@ -493,6 +493,13 @@ Ext.define('Proxmox.validIdReOverride', {
     validIdRe: /^[a-z_][a-z0-9\-_@]*$/i,
 });
 
+// use whole checkbox cell to multiselect, not only the checkbox
+Ext.define('Proxmox.selection.CheckboxModel', {
+    override: 'Ext.selection.CheckboxModel',
+
+    checkSelector: '.x-grid-cell-row-checker',
+});
+
 // force alert boxes to be rendered with an Error Icon
 // since Ext.Msg is an object and not a prototype, we need to override it
 // after the framework has been initiated