Allow configuring/reordering the band display

[grimsteel]

First, I wanted to let you know how helpful this library has been to me! The work you (and the many other people involved in this Mi Band community) have done is really amazing.

This allows configuring what items show on the band display

Usage:

from constants import DISPLAY_ITEMS

band.setBandDisplay(DISPLAY_ITEMS.ALL_ITEMS) # Show every item except MI Home
band.setBandDisplay([DISPLAY_ITEMS.WORKOUT, DISPLAY_ITEMS.STATUS, DISPLAY_ITEMS.MORE, DISPLAY_ITEMS.HEART_RATE]) # Display those items in that order

https://github.com/satcar77/miband4/blob/97e13678d07e66942a1028c72d61140f850d35af/constants.py#L108-L114

When I was looking at the BT Packets, I noticed that the app was always skipping over the display item with ID 5. When I tried making that display item visible, I got something called "Mi Home". Maybe that's a HA thing they have that's not there by default.

I'm working on adding weather support!