ViewHelper for a user contact link

[TiSiE]

We need a view helper that generates a contact link from a user entity.

$this->contactLink($user);

It should

• generate a mailto: link with the email address and using the name as link content
  <a href="mailto:email@address.net">Fancy Name</a>
• generate a mailto: link with the email address, if no name is present in the user entity.
  <a href="mailto:email@address.net">email@address.net</a>
• generate a string consisting of the name, if no email-Address is available
  Fancy Name
• generate an empty string, if no contact information whatsoever are available.

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Probably useful

• Extending Core\View\Helper\Link
• Auth\Entity\Info: Embedded document with the contact info

[TiSiE]

@sergey-galenko
It would be nice, if you can also create a unit test case for the new ViewHelper class

[sergey-galenko]

@TiSiE I added unit tests. Please review.