Add new column "StartDate" to database-file

[zulrak1]

New release 1.4.4 already has a new column "market" and has the possibility of no image in database.

For people who organize Bing wallpapers in their personal collections by market and by date, and mainly for programmers that publish Bing wallpapers in websites, it would be of tremendous importance if Bing issue date, output field "startdate" (yyyymmdd) of HPImageArchive, could be added as a new column in database-file.

tks