use streamiterator instead of std iterator

[teamplayer3]

The idea behind this is to avoid creating the CanFrame, which is used to transmit the single frames, for every frame. With the StreamIterator the frame can be initialized once per transfer and then be reused.

I did some performance tests on the different implementations for transfers and got these results (cortex-m4 170 MHz, measurements in micros):

frames	std iterator	streamiterator
1	0	0
2	3	3
3	5	4
4	7	6
5	8	7
6	10	8
7	11	10
8	12	11

This is not that much of a performance improvement. But I think for the future this could be helpful. The now used ArrayVec is very efficient in array initialization and is great for the 8 byte which are used by classic CAN. But if the transmission can send a larger payload, this could give more performance boost. As well, if we have to use a heap allocated payload somehow.

This new implementation will change the usage for transfer messages:

let mut frame_iter = node.transmit(&transfer).unwrap();
while let Some(frame) = frame_iter.next() {
    send...
}

The user gets the frame as a reference. This has no limitations. If the user needs to store the frame to send somehow later, it could be done by cloning the frame. But now the user is responsible for this.