rename writeStringToBuffer() to writeArrayToBuffer()

[ysmilda]

In my opinion this function is confusingly named as a String is typically a set of characters. I would suggest to change it to writeArrayToBuffer() as this better covers the intended purpose. This would mean a minor functionality break, but would help with readability.

Also wouldn't it be more logical to support uint16_t array's as Modbus is 16 bit values based?

[yaacov]

Don't feel strongly about it :-) I'll look at the code, and if I like it it's ok by me 🦄

[ysmilda]

As it had me really confused when I first encountered it I changed it in my latest pull request. #53