Nordpool calibration, cleanup execution code

What's Changed

Features

Improve Nordpool correlation by auto-calibrating against the current data

• Re-work nordpool to calibrate against real data by @springfall2008 in #1567
• Improve nordpool corrolation by @springfall2008 in #1568

Bug fixes

Some re-work of the code that controls the inverter execution, and unit testing added. Still needs more work to close coverage on all scenarios.

• Fix bug in set_discharge_freeze preventing freezes, unit testing by @springfall2008 in #1554
• Unit testing execute code, cleanup by @springfall2008 in #1555
• Fix error in latest merge by @springfall2008 in #1569

Documentation

• Documentation, template and minor code changes by @gcoan in #1563
• Update energy-rates.md by @stiplady in #1561

New Contributors

• @stiplady made their first contribution in #1561

Full Changelog: v8.5.1...v8.5.2