Manual tariff setting

[spetrie13]

Add a section in config file to manually specify tariff rates for both import and export and disable the octopus energy rate aquisition.

This will be usefully when moving away from octopus to another energy provider and still be able to use pv opt.

Thanks.

[fboundy]

Yes - it's been something I've been planning. Will try to add it to 3.15

[github-actions]

Stale issue message

[fboundy]

Bump