Solaredge-modbus

- Fixed breaking changed in pymodbus versions 3.4.1 and later
- Fixed unit inheritance in parent connection mode (herbi3)

* Added missing requirement (`pyserial-asyncio`) after pymodbus breaking changes

* Added missing SunSpec identifier registers (thanks ixtrader)
* Added updated SunSpec documents
* Fixed breaking change in pymodbus 3.0.0 release

* **Warning:** renamed various p1/p2/p3 registers to conform to industry wide convention to use l1/l2/l3.
* Added missing `_encode_value()` function to support writing registers.
* Fixed `example_influxdb.py` meter and battery values.

* added a number of power reduction registers (thanks fredlcore)
* parent connection unit now honored in meter and battery connection (thanks ctrl-alt-d)
* added power reduction and battery documentation
* fixed current scaling value in `example.py` (thanks rdorsch)
* migrated to newer project structure, cleaned up package files
* removed calculated values from `example_influxdb.py` (see 28)
* fixed meter scaling in `example_influxdb.py`

- allow `unit` to be overridden when a parent connection is provided (thanks binsentsu)
- correct enum test for three phase inverters in `example.py`
- added documentation for reading from multiple slaved inverters
- refactored string decoding
- added connection test to deal with new behavior in `pymodbus` >= 2.5.0