Add tool to handle entware services

[Eeems]

• Adds new rcctl command to manage entware services
• Adds new template unit that rcctl uses to start entware services with systemd
• Adds bash completions for rcctl

[Eeems]

It's probably worth pulling this into a different package that toltec-base depends on, since it should be a rmall package.

[raisjn]

what's the motivation for this?

[Eeems]

what's the motivation for this?

Allow a user to easily manage entware services with systemd since we don't use the entware init stuff. This avoids spinning up their init binary as a subprocess to manage their services, and instead uses systemd for everything.