This change implements a mechanism for executing a restricted set of commands on the host from within the screenly Docker containers by using a very simple host agent process, which requires only 2 packaged dependencies (python3 and python3-redis) from the standard Raspbian repositories.
Initially, this functionality is used to implement the previously disabled reboot and shutdown features. However, this could fairly easily be expanded to re-implement the USB asset loading functionality.
Furthermore, this change removes the reinstallation of build-essential, as /usr/lib/gcc/arm-linux-gnueabihf/4.9/cc1plus does not exist after reinstalling such and screenly builds without error.
Signed-off-by: Nash Kaminski <nashkaminski@kaminski.io>
