p-InputMask does not update its 'filled' property when use within a FormGroup

[mselerin]

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Similar closed issue : #1444

Plunkr Case (Bug Reports)
http://plnkr.co/edit/d7ZpJl

Current behavior
When InputMask is use with a FormGroup and a value is specified before the AfterViewInit hook, the filled style class (i.e. 'ui-inputwrapper-filled') is not set correctly.

See printscreen from #1444

Expected behavior
The_filled_ style class should be set whenever the model is updated, even if it's before the AfterViewInit hook.

Minimal reproduction of the problem with instructions
See the above plunkr.

What is the motivation / use case for changing the behavior?
Forms data could be retrieved before the AfterViewInit is called (for example : some default data).

Proposed fix
In the InputMask component, the filled property could be a simple getter (just like in the InputText component) instead of being updated in several places.

// components/inputmask/inputmask.ts

get filled(): boolean {
   return this.input && this.input.value != '';
}

Please tell us about your environment:
Windows 8
IntelliJ Idea 2016.3
npm
webpack-dev-server
lastest version of Google Chrome / Firefox

• Angular version: 2.4.1
• PrimeNG version: 1.1.3
• Browser: Chrome 55 | Firefox 50.1.0 | IE 11
• Language: TypeScript 2.1