Split doFlash() to do_flash() and do_download() methods.
Removed file-checking.
Merge pull request #260 from askeing/split_download_method

Split doFlash() to do_flash() and do_download() methods.
Added support of more device information (base image).
Merge pull request #269 from askeing/add_more_device_info

Added support of more device information (base image).