[i18n] Common msgid for several sources but with different context

It is impossible to translate correctly following message:

    #: ../src/common/helpers.py:87 ../src/vcard.py:249 ../src/vcard.py:251
    msgid "Unknown"
    msgstr ""

In Bulgarian (and many other languages) there are 3 genders. I should translate the above message asf:

    Неизвестно (neutral) - for helpers.py (status message)
    Неизвестен (masculine) - for vcard.py (client)
    Неизвестна (feminine) - for vcard.py (OS)

Since Gajim is in a deep freeze :-P I suggest to leave it as it is and fix it after ther release. You might want to take a look at this GNOME bug, which is another story, but with the same outcome.