Support for converting ANNIVERSARY

vcard 3 -> 4
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Find all X-ABDATE and X-ANNIVERSARY properties, and merge the ones with identical values. Convert all of these to ANNIVERSARY.

vcard 4 -> 3
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Convert ANNIVERSARY to both X-ABDATE and X-ANNIVERSARY.
PHP 5.3
Missing space.
select() all group properties without specifying the name
Support for multiple anniversaries in a vCard
remove unneeded whitespace
Merge pull request #154 from fruux/anniversary

Support for converting ANNIVERSARY