Option to let the mask return it's view value.

The mask cannot return it's view value, only the raw value.

In some cases, we would like the view value to be return.

This way we can simply just do: 
```
<input type="text" name="CellPhone" ng-model="field.Value"  
                             ui-mask="99999999" ui-mask-use-viewvalue="true" >
```