add settings.hpp for multi_download & http_stream

Signed-off-by: Jack <jack.wgm@gmail.com>
delete options.hpp, move to settings.hpp

Signed-off-by: Jack <jack.wgm@gmail.com>
improve multi_download.hpp & http_stream.hpp

Signed-off-by: Jack <jack.wgm@gmail.com>
fixed vc2012 project files

Signed-off-by: Jack <jack.wgm@gmail.com>