dbBulkWrite and binaries

[ruaridhw]

Pull Request Changes

• [x] Added new function dbBulkWrite for unloading tables directly to disk #20
• [x] Updated dll binaries from #27 and new function
• [x] Added appropriate tests for new function
• [x] Support missing strings and null values
• [x] Support bit, bigint, decimal and numeric SQL Server data types

[agstudy]

thanks!