Feature Request: undelateable

[cos2000]

Is it possible to add a option in which i can give a array with values that cant be unselected by chosen?

I actualy had a case and coded a driveby to realize. Lets say we have a mulitselect with a list of values:
1: Germany
2: USA
3: Canada

When i load the site USA (value) is preselected so chosen shows it as selected. It should be possible to say: value 2 cant be deselected by chosen, because USA MUST be in the selected list!

A simple option like:

undelateable: {2}

should be a usefull option!?