Umpqua Bank will double the contributions to its Give Back to School Fund over Labor Day weekend. The fund provides grants to K-12 schools in Oregon, Washington, California and Nevada. Since the campaign launched in early August, it has grown to $10,000 through the bank contributing a dollar for each “like” or “share” of its Facebook page. Between today and Monday, the bank will put $2 into the fund for each like or share. Umpqua Bank’s Facebook page is at facebook.com/umpquabank. The bank has set no limit on the number of contributions that can be made to the fund. Douglas …