Revert unintended change to debug level and upgrade mxt-app version output to info

Signed-off-by: Nick Dyer <nick.dyer@itdev.co.uk>
Handle file not found in config code

Fix segfault for files with no extension. Add new error return code for file
not found. Improve error handling and logging.

Signed-off-by: Nick Dyer <nick.dyer@itdev.co.uk>
Return success from --query when device found

In normal mode, the scan terminates when a device is found. In query mode, the
scan must continue, however if a device is found using any backend, return
success. Also scan USB in query mode even if sysfs succeeds in finding a
device.

Signed-off-by: Nick Dyer <nick.dyer@itdev.co.uk>