#153 Add more general dates

[Anonymous]

If all entrys with the Datatype xsd:date would also contain entrys of the type xsd:gYear, xsd:gYearMonth, xsd:gMonth, xsd:gMonthDay and xsd:gDay, that would allow search requests like "What happened on March 19" or "Who was born in May 1954". This should be a simple matter of extracting the values from the complete date and put them in the formats of gYear, gYearMonth etc.
Example: <http://dbpedia.org/resource/Brendan_James> dbpedia-owl:birthDate ?date already contains the additional entry for gMonthDay.