This commit adds W5500 W5100 and ENC28j60 drivers from @njh with credits
They are available in libraries/
An example is added in W5500 examples directory
plus:
* Extract dhcp server from lwip2 and add it to the core as a class.
It must always be present, it is linked and can be called by fw on boot.
So it cannot be stored in a library.
* ethernet: static or dhcp works
* PPPServer: example
* bring WiFi.config() to the lwIP generic interface (argument reorder common function)
* move hostname() from WiFI-STA to generic interface
* remove non readable characters from dhcp-server comments
* dhcp-server: magic_cookie is part of bootp rfc
* fixes from https://github.com/d-a-v/W5500lwIP/issues/17
* enable lwip_hook_dhcp_parse_option()
* +ethernet tcp client example in w5500 library examples
