Better logic for running without the PIco and Raspbian packages

This release adds guards against the system becoming unable to boot due to the PIco not being installed.

It does so by checking whether there ever was a HIGH on pin #27, and if not, then the pulse train will not be sent and the system will not go into shutdown. Also, the shutdown resets this, and instead of exiting, picod will now continue monitoring the FSSD signal and resume sending the pulse train on pin #22 when the FSSD signal goes back to HIGH.

This is a strict improvement over the original Python script.

Also, this release archive includes the necessary files for building a Debian/Raspbian archive, along with the init scripts to launch the daemon. The attached .deb file, also available at https://ef.gy/raw/download/debian/rpi-ups-pico_3-1_armhf.deb, is compiled for Raspbian on a Raspberry Pi.

Userspace virtual input device driver

This release adds pico-i2cd, which is a virtual user-space input device driver for the KEY_A and KEY_B buttons on the PIco. These are translated to BTN_A and BTN_B events, accordingly.

Further, KEY_F is also implemented and mapped to BTN_C (there's no BTN_F).

This is a separate daemon, as the set of permissions to run this is somewhat different and it's not strictly required for the PIco to function, as opposed to picod.

Initial Release

This is the initial release of picod, a daemon to power the UPS PIco by pimodules.com. The original script for this is in Python, which makes it bigger and it seemed like a bad idea to depend on Python being installed for your UPS to work.

See the README for installation instructions.