Samsung ASHP MIMB19N support

[glynhudson]

Adds support to Minimalmodbus (multiple meters) interfacer to read from Samsung ASHP / HVAC using via the Samsung Modbus Module MIMB19N

Example config for Samsung ASHP

[[SAMSUNG-ASHP-MIB19N]]
    Type = EmonHubMinimalModbusInterfacer
    [[[init_settings]]]
        device = /dev/ttyUSB0
        baud = 9600
        parity = even
        datatype = int
    [[[runtimesettings]]]
        pubchannels = ToEmonCMS,
        read_interval = 10
        nodename = samsung-ashp
        # prefix = sdm_
        [[[[meters]]]]
            [[[[[ashp]]]]]
                address = 1
                registers = 75,74,72,65,66,68,52,59,58,2,79
                names = dhw_temp,dhw_target,dhw_status,return_temp,flow_temp,flow_target,heating_status,indoor_temp,indoor_target, defrost_status, away_status
                scales = 0.1,0.1,1,0.1,0.1,0.1,1,0.1,0.1,1,1
                precision = 2,2,1,2,2,2,1,2,2,1,1

Main changes:

• Added option to set parity: even, odd, mark, space or none. Default is none
• Added option to set datatype: int or float, this determines if the registers are read using read_register or read_float. Default is float.
• Added option for scales to be able to scale integers to floats, default is no scale.

Note: It's not possible to read from and SDM120 at the same time as a Samsung ASHP using the same USB modbus device since SDM120 uses different baud rate and parity.