Add custom eds storage format & block transfer mechanism

[samsamfire]

Hi,

CiA defines objects 0x1021 for storing EDS and object 0x1022 for storing the format used (which suppose to be mandatory according to spec btw). I've added two optional parameters to add_node :

• block_transfer to enable or disable block transfer
• eds_format_handler, callable that takes sdo io and returns an eds file handle. The point of this is so that anyone with a specific format can handle their own logic. I've also added some documentation , an example and description for parameters.

[af-silva]

During the weekend will try to give it a look.

[samsamfire]

Bump have you had a chance to look at it ?