tools: list supported styli with the local tablet

[whot]

Example output appended now to the previous output:

devices:
- name: 'Wacom Intuos Pro M'
  bus: 'usb'
  vid: '0x056a'
  pid: '0x0357'
  nodes:
  - /dev/input/event21: 'Wacom Intuos Pro M Finger'
  - /dev/input/event18: 'Wacom Intuos Pro M Pen'
  - /dev/input/event19: 'Wacom Intuos Pro M Pad'
  styli:
   - id: 0x842
     name: 'Pro Pen 2'
     type: 'general'
     axes: ['x', 'y' , 'tilt', 'distance', 'pressure']
     buttons: 2
     erasers: [0x84a]
   - id: 0x84a
     name: 'Pro Pen 2 Eraser'
     type: 'general'
     axes: ['x', 'y' , 'tilt', 'distance', 'pressure']
     buttons: 2
     is_eraser: 'true'
     eraser_type: 'invert'
...

and for the AES pens:

   - id: 0x221
     name: 'AES Pen'
     type: 'mobile'
     axes: ['x', 'y' , 'pressure']
     buttons: 1
     is_eraser: 'true'
     eraser_type: 'button'