Flutter Sense Hat Environment Display

Make the Sense Hat Temperature, Humidity and Pressure available vie Bluetooth, and display it in a Flutter app on a phone.

See Bluetooth.md for the Bluetooth GATT UUIDs currently implemented.

The Raspberry Pi Bluetooth server is forked from Douglas6/cputemp.
My changes are to:

• Use temperature, humidity and pressure data from a Sense Hat,
• Use the official UUIDS for Environmental Sensing Service and Characteristics, and
• Encode the data as the expected list of bytes, instead of as strings.

TODO

See the GitHub issues.