FormPanel in dashboard widgets

### Problem

The original panel (the container of all widgets) initially was a FormPanel (thus created a form).
Any "subsequent" form were considered as "div", resulting in being always empty when submitted.

### Proposed solution

I changed the panel to `MODx.Panel` (without form) and added appropriate classes to get a similar look.

In addition, i saw the "recently edited resources" grid was always loaded, no matter if the widget was visible or not. Now the grid is loaded via the widget "script"