Add file logger and fix log level output (#9)

Improve logging output

Reviewed-on: #9

src/libusbwrap/interface/IUsbDevice.hpp

@@ -24,8 +24,9 @@ enum class Speed {
 
 class IUsbDevice {
    public:
-    virtual bool open()  = 0;
-    virtual void close() = 0;
+    virtual ~IUsbDevice() = default;
+    virtual bool open()   = 0;
+    virtual void close()  = 0;
 
     // libusb wrappers
     virtual bool detachKernelDriver(int interfaceNo) = 0;