Raspberry Pi OS Bullseye support

[druck13]

Raspberry Pi OS Bullseye no longer includes Python 2, so all python programs containing #!/usr/bin/env python will no longer run directly from the command line unless it is changed to #!/usr/bin/env python3.

I have not removed Python 2 support or changed the documentation, the programs can still all be run under Python 2 on older OS's by prefixing the command with python, but will run by default under Python 3.

It probably is time to remove Python 2 support completely, but I'll leave that to the author.

Additional changes:-

• Corrected direction of movement when key presses are used in the pantiltweb gui.
• Added get_pixel method for blinkt kitt example program