Rpi-backlight

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- Fixed CLI and typo

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- Added command line interface (``rpi-backlight`` and ``rpi-backlight-gui``)
- Code improvements - thanks to deets

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- Fixed ``set_power(on)`` function
- Added function to get the current power state of the LCD
- Added docstrings
- Code cleanup and improvements

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Initial release. Added necessary files and basic features:

- Change the display brightness smoothly or abrupt
- Set the display power on or off
- Get the current brightness
- Get the maximum brightness