DbfDataReader Versions Save

Thanks to @dustykline for the fix to allow DbfDataReader to be constructed with a stream reference.

Fixes reading null values. Closes #16

Adds DbfDataReaderOptions allowing skipping of deleted records and settings the encoding e.g.

var options = new DbfDataReaderOptions
{
    SkipDeletedRecords = true,
    Encoding = Encoding.GetEncoding("WINDOWS-1251")
};

using (var dbfDataReader = new DbfDataReader(FixturePath, options))
{
    while (dbfDataReader.Read())
    {
        // user code
    }
}

• Fixes encoding issues on reading string values #19

Fixes #6 DbfTable => IsClosed is inverted (thanks @djmulder)

Targets NET452 Fixes dependencies Fixes compilation warnings

Renamed to DbfDataReader to avoid conflict with NuGet package created 3 days earlier