Bug 885546 - VCF importer saves type="UTF-8" in contact fields [r=arcturus]

This Pull Request does the following things:

    Assign proper type to multi-property fields (thus solving the UTF-8) bug
    Assign proper "PREF" property to mozContact if present
    Simplify and optimize parts of the code
    Fix regression introduced by referring to navigator.mozContact instead of just mozContact.

Thanks again, @arcturus!