init: move makefile functionality to upgrader

At present, it is necessary to manually run make in `av/init` to install AusOcean software and required services.

It is proposed to have the upgrader do this instead in order to eliminate the need to log into new devices.

A new `init` bool syntax in `pkg.json` would identify components that need only be installed once and/or commands that only need to be run once.

For example, to install and enable the `rv.service`:

```
{
"name": "rv.service",
"shared": true,
"init": true,
"cmd": "cp -f $name /etc/systemd/system; systemctl enable $name"
}
```