Session manager missing objects feedback

fixes #1380

Introduces the concept of mandatory objects to the configtaskwidget framework. All objects added to the framework are mandatory by default.
An upload or save operation on a mandatory object not present on the hardware will result on a warning icon being show on the button which started it. The same operation will result on a op success icon if the object is no t mandatory.
If on the group of objects handled by the framework there is an error and a warning the error icon will be shown.
This PR also makes the button tooltip show which objects failed being uploaded, saved or are missing in hardware (if mandatory).