add usb_probe tool and improve compatibility (#33)

* add usb_probe tool and improve compatibility with older/non-compliant devices

* fix logic test

* add doc

docs/mkdocs/src/apps_and_tools/usb_probe.md

@@ -0,0 +1,38 @@
+USB PROBE TOOL
+==============
+
+This tool lists all the USB devices, with details about each device.
+For each device, the different possible Bumble transport strings that can
+refer to it are listed. 
+If the device is known to be a Bluetooth HCI device, its identifier is printed 
+in reverse colors, and the transport names in cyan color.
+For other devices, regardless of their type, the transport names are printed
+in red. Whether that device is actually a Bluetooth device or not depends on
+whether it is a Bluetooth device that uses a non-standard Class, or some other
+type of device (there's no way to tell).
+
+## Usage
+
+This command line tool takes no arguments.
+When installed from PyPI, run as
+```
+$ bumble-usb-probe
+```
+
+When running from the source distribution:
+```
+$ python3 apps/usb-probe.py
+```
+
+!!! example
+    ```
+    $ python3 apps/usb_probe.py 
+
+    ID 0A12:0001
+    Bumble Transport Names: usb:0 or usb:0A12:0001
+    Bus/Device:             020/034
+    Class:                  Wireless Controller
+    Subclass/Protocol:      1/1 [Bluetooth]
+    Manufacturer:           None
+    Product:                USB2.0-BT
+    ```