Define base addressing methodology (zero or one based)

[paulorb]

Define base addressing methodology (zero or one based)
Currently user is able on XML to configure address zero. When clients like modpoll reads from it, it will read based on (base addressing 1) so 0x:1 is associated with offset 0 (0x:0), but at the same time user is not able to specify 0x:0 on modpoll, which state that address is invalid.
Confusion described on: https://support.elkor.net/knowledgebase.php?article=14