[ticket/12680] Adds alternative text to contact icon in viewtopic.php

PHPBB3-12680
[ticket/12680] Adds second alternativ text and font-size: 0 to remove text

PHPBB3-12680
[ticket/12680] Adds alternativ text with new variable to contact:

PHPBB3-12680
[ticket/12680] Removes unnessesary $user->lang from CONTACT_USER

PHPBB3-12680
[ticket/12680] Little changes, but some issues are still there

PHPBB3-12680
[ticket/12680] Still some problems with displaying the nickname in ucp

PHPBB3-12680
[ticket/12680] Solves last bugs. viewprofile: contact --> contact nickname

PHPBB3-12680
[ticket/12680] Brings back get_username_string()

PHPBB3-12680
[ticket/12680] Adds variable for guest user

PHPBB3-12680
Merge pull request #2567 from Crizz0/ticket/12680

[Ticket/12680] - Adds alternative text to contact icon in viewtopic.php

* Crizz0/ticket/12680:
  [ticket/12680] Adds variable for guest user
  [ticket/12680] Brings back get_username_string()
  [ticket/12680] Solves last bugs. viewprofile: contact --> contact nickname
  [ticket/12680] Still some problems with displaying the nickname in ucp
  [ticket/12680] Little changes, but some issues are still there
  [ticket/12680] Removes unnessesary $user->lang from CONTACT_USER
  [ticket/12680] Adds alternativ text with new variable to contact:
  [ticket/12680] Adds second alternativ text and font-size: 0 to remove text
  [ticket/12680] Adds alternative text to contact icon in viewtopic.php