[ticket/12793] String '0' does not display for string profile fields

See https://github.com/phpbb/phpbb/pull/2647#discussion_r14503051

PHPBB3-12793
[ticket/12793] Changing get_profile_contact_value to get_profile_value_raw

Changing the return to get_profile_value_raw

PHPBB3-12793
[ticket/12793] Tests (added and changed)

changed behavieur of 0 as in and added 0 as string test

PHPBB3-12793
Merge pull request #2718 from lucifer4o/ticket/12793

[ticket/12793] String '0' does not display for string profile fields

* lucifer4o/ticket/12793:
  [ticket/12793] Tests (added and changed)
  [ticket/12793] Changing get_profile_contact_value to get_profile_value_raw
  [ticket/12793] String '0' does not display for string profile fields