Significant changes

When searching for the device name specified in the device option, FlexASIO now ignores devices that are in the wrong direction (input or output). This fixes issues with input and output devices having identical names. See #39.
Add --buffer-size-frames, --buffer-switch-count, --input-file, --output-file and --sample-rate command line options to FlexASIOTest. See #34.

Minor changes

Fix a crash when returning an ASIO error message longer than 123 characters.
Make FlexASIOTest text output I/O asynchronous to avoid blocking in real-time code paths (e.g. ASIO buffer switch callback)
Improve FlexASIOTest text output by making it display timestamps, process IDs, and thread IDs.
PortAudioDevices now outputs the PortAudio debug log to stderr (as opposed to the FlexASIO log).
PortAudioDevices now outputs device names in quotes to avoid confusion when device names end with whitespace.