Add many new boards, including QT Py. Add more placeholders.

Add WinUSB driver for USBtinyISP programmers. See #23.

NOTE: The installer executable and the drivers are no longer signed. Our signing certificate has expired, and given that Windows 7 is past end-of-life, and Windows 8.x is little used, we do not plan to renew our certificate. So you will need to approve installing an unsigned driver.