Port to Incus

[melato]

Make a version of lxdops that works with Incus instead of LXD.

[melato]

The LXD and Incus APIs are almost identical, since they are forks of each other. But they are not meant to be compatible. They are expected to diverge and they already have some incompatibilities.

I am looking into creating an interface layer between lxdops and LXD, and create implementations for LXD and for Incus. Might also rename lxdops to something else.

[melato]

I have done this as follows:

• fork this repository as lxops
• create an API for interfacing with the instance server backend
• Use this api for all commands in the CLI
• implement this API for LXD and Incus in separate repositories, lxops-lxd, lxops-incus, that will build similarly named executables.
• The resulting executables will have the same CLI usage, but each one will work with a specific backend.

I'll think about it a bit more and then publish these repositories.

This is also a good opportunity for an overall refactoring and cleanup of the commands and perhaps also of the config file format.