Abstracted fetch of adr and org elements into i_fetchStructuredProperty(..)
and removed redundant code.
Abstracted the fetching of property IDs from various link tables into
i_fetchPropertyIDsForContact(..) and removed now redundant code. Data types
do not use this mechanism yet because they currently all data types
(e.g. logo, photo) are read at once from the same table. Probably need to
adjust that behavior as it will be needed to reload changed Properties
down the road and will make some of the code more clear.
Made the behavior for fetching the data properties consistent (hiding the
differences in the SQL) so that they can be fetched by
i_getBasicProperty(..). Removed now redundant code.
Removed obsolete i_fetchCategoriesForVCard(..).