Investigate: How to make use of BLOCK_MODE in FESA

In FESA currently always recv(Block) is used. This will receive specific Block from a PLC for ALL devices. --> Actually there is no advantage in using DEVICE_MODE, since always all devices for a block are received. ( no possibility to get all Blocks of a device )

There is a method device->recv(block), but this will only get a specific block for a specific device, not all blocks !

So currently there is no advantage in using DEVICE_MODE.

We cannot just remove DEVICE_MODE, since many PLC's currently probably use it. For NI there is only the DEVICE_MODE .. there is no block-mode at all.

DEVICE_MODE currently is the default, so it is no option to remove it.

Proposal: Add support to get all Blocks of a device by method.