Merge pull request #9 from ericek111/master

move hw_flavour from the initializer into a separate API function

Recognize SDRplay RSP2

Recognize SDRplay RSP1A

Issue #1: fixed library major version

Added option to detach kernel driver like with librtlsdr

Do not libusb_close on async failure to prevent segfault

Support of mixbuffer gain in AM modes and use it properly for tuner g…

…ain setting in AM modes