Localized Labels

Localize labels passing an object with translated strings. Backward compatible because if the new attribute is not present use the default english strings.

Usage: in your module set an object like:
```
$scope.myLocalizedStrings = {
    selectAll: "Seleziona Tutto",
    selectNone: "Deseleziona Tutto",
    reset: "Reset",
    search: "Cerca ...",
    noneSelected: "Nulla selezionato"
};
```

and pass with the attribute localized-labels
```
<div multi-select
   localized-labels="myLocalizedStrings"
>
</div>
```