`show attributes` wasn't being populated since `show_attributes()` was never called.
Also updated `show attributes` to match the color and indentation of `show services`
It would be nice to pip install bumble without having to first install
the libusb system dependency. Expecially on platforms like Windows and
Mac, without a default package manager.
The libusb_package Python package distributes prebuilt libusb-1.0 shared
libraries for each OS and architecture as binary wheels for the pyusb
project. Add this package as a dependency for bumble.
For the pyusb transport, the libusb_package.find() function is a drop-in
replacement for pyusb.core.find(). It searches the libusb_package
site-path before system paths and creates a pyusb backend.
For the usb transport, use libusb_package.get_library_path() to return a
path to the libusb-1.0 library in site-packages. If this path exists,
create a ctypes DLL and init the usb1 backend. This only needs to be
done once. All future calls to usb1 will use this opened library.
If the library path does not exist, do nothing, and usb1 will search
default system paths when the usb1.USBContext object is created.
This commit pins the libusb_package dependency at 1.0.26.0 to ensure
every bumble install uses the exact same version of the libusb library.
