title: p-message(KeyFilterModule) is not a known element in Angular6
body: <p>When I trying to p-message along with KeyFilterModule from Prime-NG UI Component in Angular 6 and for reference following packages are installed:</p>
  
  <blockquote>
    <p><strong>npm -v</strong>
    6.1.0</p>
  </blockquote>
  
  <p><strong>>ng -v</strong>
  Angular CLI: 6.0.8
  Node: 8.11.3
  OS: win32 ia32
  Angular: 6.0.9</p>
  
  <p>Please find below code used and throwing the error.</p>
  
  <p>HTML File:
   </p>
  
  <pre><code>      &lt;input type="text" formControlName="UniqueNumber" class="form-control" id="UniqueNumber" name="UniqueNumber" placeholder="Patient Unique Number"
         pInputText [pKeyFilter]="ccRegex" [pValidateOnly]="true" placeholder="123-12-1234" /&gt;
         &lt;p-message severity="error" text="Not a valid number" [@errorState]="form.dirty &amp;&amp; !form.valid ? 'visible' : 'hidden'"&gt;&lt;/p-message&gt; 
      &lt;/div&gt;
  </code></pre>
  
  <p>ts code:
    ccRegex: RegExp = /[0-9]{3}-[0-9]{2}-[0-9]{4}$/;</p>
  
  <p>I understand, KeyFilterModule is newly introduced in Angular 6. Any help in regarding this highly appreciated.</p>
  
  <p>Thanks!</p>