Use erlang term based port instead of a c-node

[abelino]

Move to using port since the bacnet-stack library wants to support a single device type per instance.

[amclain]

Just look out for the one ⛔

[amclain]

Starting a new line with { is a good question for the style guide.

[abelino]

We talked through style-guide in a call and concluded the current style in this PR produces code that is easier to digest/read. This also aligns to similar styles found in the linux and zephyr codebases. i.e.

int sum(int a, int b)
{
  return a + b;
}

There are other variations of this style that aren't present in this PR but are also important to illustrate:

request_t*
parse_request_data(request_context_t *context, void *buffer, size_t length)
{
  return NULL;
}

request_t* parse_request_data(
  request_context_t *context,
  request_type_t type,
  void *buffer,
  size_t length
) {
  return NULL;
}

or

request_t*
parse_request_data(
  request_context_t *context,
  request_type_t type,
  void *buffer,
  size_t length
) {
  return NULL;
}