New Wifi dongle support

[rupertnash]

Various issues/comments suggest that new pocket wifi dongles have to be accessed via a POST with the request in the data rather than URL.

• 75 (now resolved by #77 - thanks Robin! @squishykid)

• 80

• maybe #84
• https://github.com/squishykid/solax/pull/77#issuecomment-1243974594

This makes the detection harder and perhaps requires the cartesian product of inverters and dongles?

Issue #80 prompted me to split out the method of access into a base class, but I would expect that the data received from different registers will need a different mapping onto sensor descriptions. One could hope that this will be the same mapping from indexes to meanings for the same model inverter meaning that part can live as a mixin and then the concrete types can just inherit from both InverterPostData and that?

I'm afraid I don't have the time right now to contribute but if tagged in a PR I am happy to run a test against my inverter (X1 Hybrid G4 with new wifi dongle - it returns gives version 3.003.02)

[jaykijay]

See also #88. The new Method via POST request works for my X1 Mini, too, i patched it myself in my own fork.

[squishykid]

resolved in 96