Add new driver for itron heat meter

[Andi252]

The pull request adds a new driver for an itron heat meter. See discussion #1081.

The meter is called UltraMaXX
and the RF module is called EquaScan hMIU RF

was extended to #1054

[Andi252]

How are the defines for dd-mfct fields created? My meter produces the id 9726 (ITW) and the meter from #1054 creates the id 97a6. I could add this second meter into the driver, but I don't know how to add the second id.

[Andi252]

The Itron-Meter from #1054 produces a dd-mfct of 97a6 which decodes into MANFCODE('i','T','W'), when I add this MANFCODE('i','T','W') to my driver the frame from #1054 is decoded and detected correctly.

@weetmuts do you know of other meters where the MANFCODE is not produced from upper case charaters?
Should I add a funktion with "normalizes" the dd-mfct before matching?

[Andi252]

I tried to find a definition of the mfct in the offical OMS specification. But the only definition I could find was the "3 times upper case letter" which I would interpret as 3 * 5 bit => 15 bit of total length. In the frame the space available is 16 bit. I couldn'f find a special purpose of this additional bit. Therefore any mfct value should be between 'AAA' = 1057 or 0x0421 and 'ZZZ' = 31710 or 0x7bde.

Unfortunately I could find several test frames in the code which have values > 31710.

@weetmuts What is the best way to handle these invalid frames?

[Andi252]

@weetmuts do you need any additional information to accept the pull request?