The widget should accept the disabled option.
In that case, CSS class "disabled".
In addition, after click dropdown will not be shown.
Also, the option to disable a specific value in a dropdown is included
In newer Embers jQuery is removed. There is a `find` but it only returns
one element and not a jQuery selector. This patch migrates our code to a
new helper `queryAll` which allows us to remove the global.
This is where they should be as far as ember is concerned. Note this is
a huge commit and we should be really careful everything continues to
work properly.
