Support constant fields

[msteiger]

Many of Wolf's proprietary messages have a constant suffix. Here's an example:

3003502309d8420104005d010000

from 30 to 03,
the "Wolf-Write-Command": 50 23
9 bytes following
The crc8 of the following 8 bytes (see #167)
The ID for "HG07" (Heizgerät Parameter 07) 42 01
The actual value: 04 00
The constant 4-byte suffix: 5d 01 00 00

I can specify it as a unsigned integer to make it work, but it's actually a constant. So I suggest adding a constant field type, together with some way of defining the constant. Maybe in the "divider/values" column?

[john30]

already available, e.g. use HEX:4,=5d010000

[msteiger]

Oh, that's perfect. Thanks for helping me out.